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\title{Digital Audio in the Library}
\author{Richard Griscom}
\date{June 2006 \\ version 1.11 [19 July 2006]}
\begin{document}
\maketitle

\tableofcontents

\part*{Preface}


In his 1966 article presenting the material---the ``stuff,'' as he
called it---of music libraries, James B. Coover described the trio of
books, scores, and sound recordings as the ``meat and potatoes'' of
music library collections. While the book and score had been around for
centuries, the ``record'' was the new kid on the block, and by the
mid-1960s---several years after the introduction of the long-playing
record---this kid had proved to be a handful, demanding of time and
resources. Coover longed for the ``halcyon days'' when librarians had to
deal ``only with 10- and 12-inch 78 rpm records, single- and
double-sided, inside-out or outside-in, made of acetate or
shellac.... But they are gone, and even though the variety of records
available then presented some difficulties, the problems were in no way
comparable in breadth or depth to those encountered today.''
\footnote{James B. Coover, ``Materials of a Music Library,'' in \emph{Manual
of Music Librarianship} (Geneva, N.Y.: Music Library Association, 1966),
3.}

And that was over forty years ago, long before the onset of the
cassette, eight-track tape, compact disc, minidisc, and digital audio
tape. Throughout the relatively brief life of the sound recording, this
hyperactive and needy member of the music-library family has been
showered with attention by its weary guardians. While the format and
content of books and scores have remained relatively unchanged over the
course of centuries, near constant innovation in sound-recording
technology has caused upheavals in collection development and facility
planning at least every few decades. Large collections and costly
equipment have been rendered obsolete as one format has succeeded
another.

Until recently, these technological innovations have been realized
through the introduction of new physical media---discs with grooves,
magnetically charged tape, microscopically pitted aluminum discs. As
each new format arrived on the scene, librarians met it with a mix of
excitement and wariness. The excitement came from considering what the
new technology offered---in most cases, enhanced fidelity, ease of use,
and storage. The wariness came from calculating the expense of adopting
the new format. Librarians approach new technology with deliberate
caution, since the potential impact on collection budgets, shelving
space, and facilities is great. It makes little sense to adopt a new
format until it is clear the format has staying power. For this reason,
libraries have usually been slow to embrace new technology, and a
healthy skepticism has allowed them to avoid being stuck today with
legacy collections of 8-track tapes and minidiscs.

During recent years, the development of digital sound technology has
taken the sound recording down a new path. Advances in computer and
networking technology have allowed the sound recording to take on a
virtual existence, and the sound recording is no longer confined to a
physical object---something to be purchased, stored on a shelf, and
circulated. It is now also a file of data---something to stream over the
internet, to download onto an iPod.

The benefits have been great. The listener is now off the leash, able to
listen anywhere there is a network connection, and with the growth of
wireless access points, the options increase daily. Librarians are also
great beneficiaries, since we can now offer substantial collections of
commercial sound recordings without the inconvenience of finding space
to store them, and we can provide reserve listening services that make
it possible for dozens of class members to listen to the same Bach fugue
simultaneously---and scattered across campus---just hours before an exam.

The challenges and frustrations continue, however. Lying behind these
digital audio services is technology that can be confounding. When
working with a collection of physical sound recordings, we could meet
listeners' needs simply by providing equipment for the various media in
our collections and making sure our collections were properly cataloged
and shelved. With digital audio, our role in bringing the music to the
listener can be far more complex. For small-scale digital audio
installations supporting curricular listening, a librarian might be
expected to encode sound recordings for curricular listening, to
maintain the server that stores and delivers the audio files, and to
create a user interface for listeners to locate and select files for
listening.

The technological knowledge and skills needed to manage digital audio
services can be daunting. Sound can be captured in a number of digital
formats and then compressed for network delivery in an even larger
number of other formats. Librarians who are new to digital audio may
find themselves grappling with technical concepts that are foreign to
them---bitrates, codecs, streaming---and feel unequipped to provide the
services that digital audio technology makes possible.

\section*{Scope and Organization}

In summer 2005, John Anderies approached me about working with him on
writing a book for librarians on digital audio and digital audio
services.  Because of other commitments, John wasn't able to see the
project to its end, but the scope and organization of this text is the
product of the planning we did together in fall 2005.  John also drafted
a few sections of this document, and for these his byline is indicated
in the heading.

This draft is an incomplete realization of the book John and I had
planned.  We had worked out a tight deadline for writing the book,
because we knew that the rapid changes in digital audio would mean that
the parts of the book would become obsolete quickly. Once John realized
he would not be able to finish the project, I decided that if the
sections I had written were to be of any use at all to readers, the text
needed dissemination quickly.  There would be no time for me to complete
the book on my own or to bring another author into the project. For
these reasons, I decided to deposit the book in
\emph{Scholarly}Commons@Penn (\url{http://repository.upenn.edu}) under a
Creative Commons license, so that others could make use of my work and
perhaps even build upon it.

The book is intended to serve as a guide and reference for librarians
who are responsible for implementing digital audio services in their
libraries. In the treatment of technological matters, I have tried to
keep the novice in mind as the primary reader, but I also hope that a
librarian approaching the book with some knowledge of digital sound
technology will find the content valuable as a reference.

The book was written to serve several purposes:
\begin{itemize}
  
\item to introduce the concepts of digital sound recording technology
\item to compare various common digital audio formats and offer guidance on their strengths and weaknesses
\item to describe the process of encoding and compressing sound
\item to explain the various ways sound can be delivered and listened to over networks
\item to survey current practices in digital audio services in libraries
% \item to examine current trends in digital audio technology and
%  speculate on their future.

\end{itemize}

This book is divided into two parts. Part 1, ``Digital Audio
Technology,'' covers the fundamentals of recorded sound and digital
audio, including a description of digital audio formats, how digital
audio is delivered to the listener, and how digital audio is
created. Part 2, ``Digital Audio in the Library,'' covers digitizing
local collections, providing streaming audio reserves, and using digital
audio to preserve analog recordings.

% Chapter 3, ``Looking toward the Future,''
% examines current trends in digital audio and gazes into the crystal
% ball. 
The appendix offers resources on copyright issues affecting digital
audio services, and the book concludes with a glossary, bibliography,
and index.

\section*{Acknowledgments}

I thank the following music librarians who responded to a call for
volunteers to complete a questionnaire on digital library services,
announced on MLA-L in November 2005: Leslie Anderson (California State
University, Long Beach), Jane Beebe (Amherst College), Leslie Bennett
(University of Oregon), Sara J. Beutter (Vanderbilt University), Linda
Blotner (University of Hartford), Anita Breckbill (University of
Nebraska--Lincoln), Pamela Bristah (Wellesley College), Ken
Calkins (University of California, San Diego), Sarah Canino (Vassar
College), Kathy Carbone (California Institute of the Arts), Alexander
Cari (Texas Christian University), Paul Cauthen (University of
Cincinnati), Keith D. Eiten (Wheaton College), Linda Fairtile
(University of Richmond), John Gibbs (University of Washington), Jon
Haupt (Iowa State University), Raymond Heigemeir (Stanford University),
Barbara Hirsch (University of California, Santa Barbara), David Hunter
(University of Texas at Austin), Amber C. Johnson (Mansfield
University), Carolyn A. Johnson (Connecticut College), Pam Juengling
(University of Massachusetts, Amherst), Karen Jung (Southeastern
Louisiana University), Rebecca Littman (University of
Wisconsin-Milwaukee), Amanda Maple (Pennsylvania State University),
Paula Matthews (Princeton University), Erin Mayhood (Boston University),
Nancy Nuzzo (University at Buffalo), Jennifer Ottervik (University of
South Carolina), Antoinette Powell (Lawrence University), Mary
Prendergast (University of Virginia), Alisa Rata (Southern Methodist
University), Tracey Rudnick (University of Connecticut), Darwin Scott
(Brandeis University), Kristina L. Shanton (Ithaca College), Bradley
Short (Washington University), Gerald A. Szymanski (Eastman School of
Music), Robert D. Terrio (Westminster Choir College), Christia
R. Thomason (North Carolina School of the Arts), Sha Towers (Baylor
University), Kent Underwood (New York University), and Marlene Wong
(Smith College). I also thank Jim Farrington (Eastman School of Music)
for sharing chapters of his Audio and Video Equipment Basics for
Libraries (2006) in advance of publication.

This draft was written mostly on the SEPTA R2 train en route from
Wilmington to Philadelphia, where I work at the University of
Pennsylvania.  Most of the research, thinking, and reflection about
digital audio that informed the text occurred at home in Wilmington, and
throughout my year's work on this draft, my wife, Lisa, was a constant
source of support, encouragement, and patience.

\begin{flushleft}
Richard Griscom \\
Wilmington, Delaware \\
June 2006
\end{flushleft}



\part{Digital Audio Technology}

A librarian does not necessarily need a thorough knowledge of the
technology of digital audio in order to plan and manage digital
audio projects and services. In larger institutions, library systems
support staff or the institution's information technology
department will have sufficient expertise with the technical side of
digital audio to make informed decisions. Even with excellent technical
support, however, a librarian managing a digital audio service will
benefit from a basic understanding of the underlying technology. A
librarian equipped with knowledge of key concepts will be prepared to
work more effectively with technical staff, who are not always aware the
issues that must be considered in providing service to library users. In a
smaller institution with limited technical support, the librarian may
have little support and be expected to manage every aspect of a digital
audio project, from staff supervision right down to selecting sampling
rates and streaming speeds. In these cases, technical expertise is
essential.

This part provides an overview of the technology of recorded sound and
digital audio, including a description of digital audio formats, how
digital audio is delivered to the listener, and how digital audio is
created.

\chapter{Fundamentals of Recorded Sound}

The sound waves that occur in nature---the clang of a bell, for example,
or the roar of a passing train---are continuous, without interruption and
without measure. These sound waves are variations in air pressure,
generated by something vibrating, such a violin string set into
rapid motion by a bow, or the halves of a bassoon reed that quickly beat
against each other whenever a stream of wind passes through them.

\section{Analog and Digital Sound}\label{ads}

Beginning with Edison's invention of the phonograph in 1877, a number of
technologies have been used to capture and reproduce sound waves, and
they fall into two broad categories: analog and digital. To understand
the difference between analog and digital, let's think for a minute
about a clock, which is probably the most common example of a technology
with both analog and digital equivalents.

Imagine an analog wall clock with the three traditional hands,
designating hours, minutes, and seconds. The hands move smoothly; as the
second hand sweeps around the dial, the minute hand makes its almost
imperceptible progress from one-minute mark to the next. The motion of
the clock is like time itself, smooth and without interruption.

Digital clocks measure time in precise increments. They convey no sense
of the smooth flow of time; the digits representing the seconds change
instantly, one after another, and after sixty seconds have passed, the
minute digit increments immediately. A digital clock chops up the
uninterrupted flow of time into precise units---hours, minutes, seconds,
tenths of seconds, and even hundredths or thousandths of seconds.

The contrast between the analog clock and the digital clock has a
parallel in analog and digital sound technologies. The motion of sound
waves, like the passing of time, is continuous; sound waves, by nature,
are analog. Analog equipment, such as Edison's
tinfoil-wrapped cylinder, are able to record and reproduce sound as
continuous waveforms. Like the motion of the analog clock, the
representation of sound on the cylinder is smooth and
uninterrupted. Digital audio equipment, on the other hand, divides the
continuous sound waves into discrete samples, captured at precise
intervals, just as a digital clock divides time into precise
intervals. When the sound is played back, the samples are reproduced in
sequence at the same precise intervals, creating the illusion of
continuous sound waves.

\section{Capturing Sound}

Any sound intended to be stored as a sound recording---analog or
digital---must first be captured. Sounds that are produced naturally---a
child's voice, a piano, the rustling of leaves, a brass band---are captured using a microphone. The variations in air
pressure that make up the sound hit a diaphragm in the microphone and
cause it to vibrate sympathetically. The vibrating diaphragm creates a
weak series of voltage pulses that are transmitted through the wires of
the microphone to its plug.

The sound captured using the microphone can be stored in a number of
ways. The microphone input can be routed to a recording component, such
as a tape deck, where the voltage pulses are stored as magnetic patterns
on tape, or to an analog-to-digital converter, which converts the
voltage pulses into a series of binary digits that can be stored on a
compact disc, DVD, DAT, or hard drive.

Most digital-audio projects do not involve capturing natural
sound.\footnote{An example of an exception would be an audio reserves
project for which the instructor provides a spoken introduction or
announcement for each audio example.}  Instead, they take existing
recordings---commercial recordings, recordings of local concerts and
lectures, field recordings captured by researchers---and convert them
into digital audio files, which can then be stored, duplicated to media
for playback, or delivered over networks.

For audio that is already in a digital format, no capture or conversion
is needed. The process involves simply reading the binary digits on the
source recording and copying them to another medium.

The sound on an analog recording, however, must be converted to digital
audio. A microphone is not used to capture the audio, because the sound
waves are already represented as a series of voltage pulses on the
analog recording. The analog sound is reproduced on a traditional audio
component (typically a turntable or tape deck), and the resulting analog
signal is routed directly to a computer or digital audio recorder for
conversion and storage as digital audio.

\section{Reproducing Sound}

The process of reproducing sound reverses the process of capturing
it. Analog recordings contain physical representations of voltage
pulses---as grooves on a disc or magnetized patterns on tape---and these
are read by an audio component and converted into voltage pulses. For a
digital recording, the binary digits are read by a digital component---a
CD player, DAT deck, computer, or personal digital player---and
translated into voltage pulses by an digital-to-analog converter.

\subsection{Speakers}

The voltage pulses produced by an analog or digital component are sent
to an amplifier and then to headphones or speakers. A speaker consists
of a coil of wire attached to one or more cone-shaped diaphragms. When
the voltage pulses are received by the coil, they are converted to
magnetic pulses that attract and repel the back of the speaker cone. The
motion of the speaker cone creates variations in air pressure that
reproduces the sound captured and stored on the sound
recording. Low-frequency sounds require that the speaker cone move
slowly, and high-frequency sounds require rapid movement. Because no
single cone size can move both slowly and quickly enough to cover the
full spectrum of perceivable sound, speaker systems often consist
multiple cones that are optimized for specific frequency ranges. The
typical categories are the woofer (25 Hz-300 Hz), midrange speaker (800
Hz-16 kHz), and the tweeter (6 kHz-30kHz). Computer sound systems often
consist of two small midrange speakers and a ``subwoofer'' to
reproduce lower frequencies.

\chapter{Fundamentals of Digital Audio}\label{fundamentals}

\section{Concepts}

The basic process of digital recording can be described simply: sound is
captured thousands of times each second, the captured samples are
converted to digital data, and the data is stored to a device. To play
back the digital sound, the process is reversed.

Underlying this basic process are a number of more complex concepts, and
understanding them will help you make informed decisions that will
improve the quality, usability, and longevity of the digital audio files
you create.

\subsection{Sampling}

When sound is recorded digitally, ``snapshots'' are taken of the analog
sound at precise intervals. The snapshots are then processed by an
analog-to-digital converter (ADC), which translates the analog sound
into binary bits that can be stored on a disc, memory chip, or some
other digital medium. The snapshots are called ``samples,'' and the process
of capturing and converting the samples is called ``sampling.''

Here is another way to look at the concept of sampling. Think of a
bouncing ball. As we watch the ball, its motion is continuous and
smooth. If we want to capture the image of the bouncing ball to view
later or to share with others, we might film it with a movie camera. As
we film the ball, the camera takes a rapid sequence of still
photographs. In fact, it takes twenty-four photographs each second. Once
the film is developed, we can see by looking at the strip of film that
each photograph shows the ball frozen at a specific point in its
continuous motion, up and down. When the film is run through a
projector, these still images are reproduced in their original sequence,
twenty-four images per second, recreating, through illusion, the
continuous and smooth motion of the bouncing ball.

When we sample sound, we take thousands of ``snapshots'' of the sound
each second, and when these samples are played back in sequence, the
resulting sound creates an illusion of smoothness and continuity, like
the illusion of smooth motion in the film of the bouncing ball.

The two parameters of sampled sound that most directly affect its
quality are its sampling rate and its resolution (or bitdepth).


\subsubsection{Sampling Rate}

The sampling rate is simply the number of samples captured each second,
usually measured in kilohertz (kHz), or thousands of samples per
second. The audio on a compact disc, for example, is sampled at a rate
of 44.1 kHz, so 44,100 samples are taken each second.

Thinking again of our motion picture of the bouncing ball, imagine two
movie cameras: one that takes forty-eight photographs each second and
another that takes only twelve photographs each second. The first
camera, because it samples at a higher frequency, will more
faithfully reproduce the continuous motion of the ball's
movement than the second camera. The same is true of the sampling rates
for sound. The more samples per second, the higher the fidelity of the
sound.

When selecting a sampling rate for audio, something known as the Nyquist
Theorem comes into play. In 1927, an AT\&T physicist named Harry Nyquist
determined that the sampling rate must be at least two times the highest
frequency to be reproduced.

Because human hearing can perceive frequencies no higher than 20 KHz,
according to the Nyquist Theorem, sampling at just over 40 KHz will
capture the full spectrum of perceivable sound. Similarly, since the
frequencies of human speech typically lie under 3 KHz, spoken word can
be sampled effectively at a far lower rate. A sampling rate of 8 KHz is
more than sufficient for recorded speech.

\subsubsection{Resolution (Bitdepth)}

When filming our bouncing ball, we want the camera to take a sufficient
number of images per second to reproduce the ball's smooth motion, but
we also want each of the images to be distinct and clear so that the
ball itself is reproduced as realistically as possible. This is
resolution.

Imagine we are using a digital video camera to capture the series of
images of the bouncing ball. The larger the number of pixels used for
each image, the clearer the ball will be. If we use a small number of
pixels---a low resolution---the ball will be fuzzy and indistinct. The
higher the resolution, the more realistic the resulting images, and the
more convincing the representation of the ball as it bounces.

Resolution in uncompressed digital audio is similar to resolution in a
digital photograph. The larger the number of bits used to capture each
sample of the sound, the higher the fidelity of the reproduced
sound. Digital audio samples are stored in strings of bits called
words. The number of bits in each word determines the resolution, or
bitdepth, of the digital audio. Typically, the lowest resolution used for
digital audio is 8 bits. Compact-disc audio has a resolution of 16 bits,
but professional recording studios capture sound using 20-, 24-, and
even 32-bit resolutions.

As in digital photography, the trade-off with resolution is storage
space. The higher the resolution, the more storage required. Also, for a
stereo recording, each channel is sampled separately, so a single sample
requires two words. You can use this formula to calculate the size of an
uncompressed audio file: \emph{size in bytes} = \emph{sampling rate}
$\times$ \emph{resolution} $\times$ \emph{number of channels} $\times$ \emph
{number of seconds} / 8 (the number of bits in a
byte)\label{formula}. For example, to calculate the size of a file
containing one minute of stereo compact disc audio: 44,100 (sampling
rate of 44.1 kHz) $\times$ 16 (resolution, in bits) $\times$ 2 (channels)
$\times$ 60 (seconds) / 8 (bits in a byte) = 10,584,000 bytes, or
10.1 MB.\footnote{One megabyte is 1,048,576 rather than 1,000,000
bytes. For more information on the confusing math of bits and bytes, see
MB, Mbps, and MHz in the glossary.}

\subsubsection{Bitrate}

The concept of resolution cannot be applied to compressed audio, since
the software doing the compression may adjust the resolution to suit the
content of the sound.\footnote{Bruce and Marty Fries, \emph{Digital
Audio Essentials,} (Sebastopol, Calif.: O'Reilly, 2005), 175.} A passage
played by a full symphony orchestra, for example, would require more
bits than a passage played by a solo oboe, simply because the sound is
more complex. For compressed files, instead of measuring bitdepth we
measure the bitrate, or the number of bits used to store a second of
sound. Bitrates are measured in thousands of bits per second (kbps), and
as with resolution, the higher the bitrate, the better the sound. The
bitrate for a typical MP3 file is 128 kbps.\footnote{It is also possible
to calculate the bitrate of uncompressed audio. The compact disc audio
example covered in the preceding section has a bitrate of 1,411 kbps
(44,100 samples per second $\times$ 2 channels $\times$ 16 bits per sample), or about
eleven times the bitrate of typical 128 Kbps compressed audio.}

Here is a useful formula to calculate the size of a compressed audio
file: \emph{size in megabytes} = \emph{number of seconds} x
\emph{bitrate in kbps} / 8,388.608 (the number of kilobits in a megabyte). Using
this formula, one minute of audio compressed at 128 kbps would have a
size of .9155 MB (60 seconds $\times$ 128 kbps / 8,388.608).

\chapter{Formats for Digital Audio}

Once audio has been sampled and converted to digital data, it can be
processed and stored in a number of different formats. During the early
development of digital audio, sound engineers devised formats for
sampling and storing audio data that met the particular requirements of
whatever operating system they happened to be using, and as a result,
multiple formats emerged for the storage of digital audio.

As time passed, certain formats gained enough of a following to become
de facto standards for certain applications.  During the 1980s, with the
advent of the personal computer, microprocessors increased in speed and
capacity, and then during the 1990s, network access became commonplace,
and new formats were developed to make the most of these technological
advances as well as to meet emerging needs for compressed streaming
audio and streaming media. Instead of the technology settling down to
one or two established formats---as has happened with audio and video
media in the past---the number of formats has increased rather than
decreased.

A regular user of the internet confronts dozens of media formats for
audio and video, and at this point, it seems doubtful that any one
format will prevail. Fortunately, today's software can play
files in most of the standard formats and files can be easily converted
from one format to another.

In this section, we will review the formats used to capture, encode, and
store digital audio. Of the dozens of audio formats that have been
developed through the years, many are now used only infrequently, so we
will look only at those that are likely to have some application in a
library setting.

\section{Terminology}

Terminology sometimes becomes blurred in discussions of digital
audio. Often the same name is applied to the software that creates the
audio, the computer algorithm that compresses and decompresses the
audio, the file format that is used to store the compressed audio data,
and the player that plays back the resulting audio file. For example,
the Windows Media Encoder can be used to create compressed Windows Media
Audio data stored in a Windows Media Audio (\texttt{.wma}) file, which can be
played back using a number of different players, including the Windows
Media Player. As I discuss digital audio, I will try to maintain
distinctions in the terminology used for file formats,
compression/decompression algorithms, software, and players. Here is a
summary of the terminology used in this book:
\begin{description}
\item \emph{digital audio data:} the binary data that represents the audio 
\item \emph{digital audio format:} the format of the digital audio data
\item \emph{codec:} a computer algorithm used to compress and decompress digital audio data in a particular audio format
\item \emph{digital audio file:} a file containing digital audio data
\item \emph{digital audio file format:} the format of a digital audio file
\end{description}

The most common area of confusion lies in the term ``format.'' A
distinction should be made between the format of the digital audio file
and the format of the digital audio that the file contains. Think of a
pitcher containing a beverage: a pitcher is similar to an audio file.
Instead of a beverage, an audio file contains audio data.  Similarly,
the type of pitcher (round or octagonal; plastic or glass) would
correspond to the file format, and the type of beverage (lemonade, iced
tea, margaritas) would correspond to the audio format. The file format
and the audio format are different concepts, and they exist
independently of each other.\footnote{A good example is the QuickTime
file format, which can contain data in a number of different
formats---for example, MP3 data or AAC data.}

\section{Structure of an audio file}

An audio file consists of several parts: a header, the audio data, and,
optionally, metadata and a wrapper. The header provides information
about the data in the file---the sampling rate, number of channels, bit
depth, and similar technical specifications. The audio data---the bits
representing the samples taken of the audio---make up the bulk of the
file. Audio files may also include metadata---text describing the content
of the audio file (performer, copyright information, track name, source
album, etc.)---and a wrapper, which controls use of the file. Digital
rights management and streaming capability, for example, are usually
provided by a wrapper.

\section{Open and proprietary formats}

Some digital audio formats are open, which means that the specifications
of the format---how the data is structured, the algorithms used to encode
the data---are freely available, and use of the format is free of legal
restrictions. Usually open formats are maintained by a national or
international standards organization. Advocates argue that use of open
formats will help guarantee long-term access to data and encourage
cooperative development of the formats.

Other formats are proprietary; for these, a private concern---usually a
commercial enterprise---maintains control over the format and the release
of details on its structure, encoding, and decoding. In many cases, the
owner of the format will release information on the structure of file
and how it is encoded but retain rights over the decoding
algorithm. Owners of proprietary formats are interested in promoting use
of their format and often take actions to discourage the use of
competing formats.

Some proprietary formats are actually based on open formats. Apple, for
example, sells tracks on its iTunes Music Store in a proprietary format
that uses AAC-encoded audio (an open format) with a proprietary digital
rights management wrapper that restricts use of the file.

Many popular, well-established formats are proprietary, and librarians
often choose to base their digital audio services on proprietary formats
because they are familiar to patrons, and software to play back the
files is readily available---sometimes even packaged with the computer's
operating system. There are some risks, however, in basing audio
services on proprietary formats. Support can be very good until the
sponsoring company abandons or alters the format. Companies often
promote their own proprietary audio formats to the detriment of others
with the hope of securing a greater market share, and they make adoption
of their format attractive by offering convenient tools for encoding
sound in the formats. Often proprietary formats are developed for
specific hardware and software, which will place limits on the playback
options for listeners. For these reasons, a proprietary format that
works well on one operating system may present problems for another.

\section{Uncompressed formats}

There are two broad classifications of audio formats: uncompressed and
compressed. For uncompressed formats, the audio data consists of the
digital audio samples as they were originally captured at their original
bitdepth. Uncompressed formats do the best job of capturing and
reproducing sound, and for that reason they are used extensively in the
recording, mastering, and storage of digital audio. In this section, we
will review the most common formats for uncompressed digital audio.

\subsection{PCM}

Pulse Code Modulation (PCM) is the process most often used to transmit
and store uncompressed digital audio data. Most uncompressed digital
audio file formats---including WAV, AIFF, and CDDA---use PCM as the
format for the audio data. PCM is not new technology; it was developed
in 1937 by British engineer Alec Reeves while working for International
Telephone and Telegraph.\footnote{Ken C. Pohlmann, \emph{Principles of
Digital Audio,} 5th ed. (New York: McGraw-Hill, 2005), 52-53.}

When an analog-to-digital converter translates analog audio samples into
binary ``words,'' it uses PCM to transmit the individual bits of the
words as voltages (``1'' as a positive voltage; ``0'' as the absence of
voltage), which can then be reconstituted as binary data for storage in
a computer file or on a compact disc. PCM is the audio equivalent of
ASCII text; because of its simplicity, most audio programs can play
PCM.\footnote{Fries \& Fries, 159.} It can accommodate a number of
different resolutions (8-, 16-, and 24-bit depths are common), sampling
rates (usually between 22 kHz and 96 kHz), and channel configurations
(for example, mono, stereo, and 5.1 surround sound).

\subsection{Sun/NeXT (extension \texttt{.au} or \texttt{.snd})}

The \texttt{.au} file format---``au'' is short for ``audio''---was
developed by Sun for use with telephone transmissions processed by Unix
computers, and it became one of the earliest formats commonly used for
audio files on personal computers. It is now primarily only of
historical interest. The extension \texttt{.snd} is used for files in
this format on Sun, NeXT, and Silicon Graphics computers. Although
\texttt{.au} files usually contain PCM audio, the format can also handle
several compressed formats.\footnote{Pohlmann, 569. For details on the
structure of the header of an \texttt{.au} file and the audio formats it can
accommodate, see \url{http://en.wikipedia.org/wiki/Au\_file\_format} 
(Accessed 28 November 2005).}

\subsection{AIFF (extension \texttt{.aiff} or \texttt{.aif})}

The Audio Interchange File Format (AIFF) was developed by Apple for use
with the Macintosh, but it is recognized by a number of Windows and
Linux audio editing programs as well. AIFF accommodates uncompressed PCM
audio with a variety of channels, sampling rates, and resolutions.

\subsection{WAVE (extension \texttt{.wav})}

The WAVE (Waveform Audio) is a proprietary file format developed by
Microsoft for use in Windows 3.1. It is actually a variant of the RIFF
bitstream format and is a ``wrapper'' format capable of containing audio
data of various types, including compressed audio data. The default (and
most common) type of data contained in a WAVE file is PCM data, which
can be accommodated in a variety of channels at various sampling rates
and resolutions.

WAVE is the format most frequently used in Windows operating systems for
uncompressed audio. Many compact disc ``ripping'' applications store the
resulting raw data in WAVE format, so it is often used as an
intermediate format when preparing compressed audio for streaming.

\section{Compressed formats}

Because uncompressed audio files are so large---about 10 MB of storage
for every minute of CD-quality audio---they are impractical for streaming
and downloading over the internet.\footnote{In order to stream CD-quality audio (two channels sampled at 44.1 
kHz with 16 bytes per sample) a computer would need to receive a 
stream at 1.4 Mbps.  Broadband networks will undoubtedly eventually 
achieve this speed, but in 2006 downloading a minute of CD-quality 
audio over a relatively fast 768 kbps DSL connection takes nearly two 
minutes (110 seconds).} For network use, audio files are
``compressed'' to reduce their size, allowing for quicker downloads and
real-time streaming.

Computers compress and decompress audio data by using software called a
codec (COmpress/DECompress). Sometimes the term ``codec'' is used
interchangeably with ``audio format,'' but there is an important
difference: a codec is software that is used to interpret an audio
format. In fact, in some cases several different codecs exist to
compress and decompress a single audio format.

With compression, there is a tradeoff between file size and sound
quality. Codecs that provide high levels of compression discard parts of
the original audio to reduce the amount of data. The more data that is
discarded, the smaller the audio file, but the loss of data also results
in a degradation in sound quality.

Audio compression formats fall into three groups: formats defined by
international standards (such as MPEG), proprietary formats (such as
Windows Media and RealAudio), and open-source formats (such as Ogg
Vorbis).

It is important to select the compression format that best meets your
particular needs, and those needs often concern more than audio
quality. The projected longevity of the format, its market share, its
technical support, the requirements and limitations it imposes on
hardware and software---all of these can be just as important as sound
quality.

\subsection{``Lossless'' Compression}

Some compression formats are able to reduce the size of an audio file
without discarding any data. This is lossless
compression.\footnote{General compression algorithms for computer
data---such as PKZIP and the Unix command \texttt{gzip}---can be applied
to audio data files, but they typically reduce an audio file's size by
only 10 to 20 percent.  Lossless audio compression formats use
algorithms specific to audio data that produce higher compression rates,
generally reducing the size of a file by between 30 and 50 percent.}
When the resulting compressed file is decompressed, it is identical to
the original uncompressed audio file. Lossless compression can be used
to distribute and archive digital audio, and digital players can decode
the most common audio formats for playback. The rate of reduction varies
generally between 25 percent and 50 percent, depending on the content of
the source file.

Because they reduce the size of an average compact-disc audio file by no
more than 50 percent, however, lossless compression formats are
generally impractical for use in streaming---at least over networks
slower than 600 kbps. Their primary application is in the archiving of
master recordings, where it is essential both to preserve content and to
save storage space. With lossless compression, if the original media is
lost or damaged, an exact duplicate of the original can be recovered at
any time.

Most lossless encoders offer various levels of compression. The tradeoff
is between file size and the amount of time required to encode a file;
higher compression comes at the cost of speed. Often the encoding
software will offer guidance in selecting an appropriate compression
level to suit your needs.

\subsection{Open formats}

\subsubsection{FLAC (extension  \texttt{.flac})}

The Free Lossless Audio Codec (FLAC) was developed by the Xiph.org
Foundation and is a free, open-source format that has no restrictions on
use and no licensing fees. There is also a metadata component: a ``cue
sheet'' metadata block can be used to store a compact disc's track
listing and index points. FLAC can be used with any PCM data with
bitdepths from 4 to 32, sampling rates from 1 Hz to 1 MHz, and one to
eight channels.\footnote{Pohlmann, 472.} Typical compression rates run
between 30 and 50 percent A technical strength of FLAC is its ability to
be decoded quickly, which makes it suitable for streaming over fast
networks. FLAC data is often contained in Xiph.org's Ogg file
format.\footnote{See also ``Ogg Vorbis'' on p.~\pageref{ogg} below.}

\subsubsection{WavPack (extension \texttt{.wv})}

As its name suggests, WavPack is used to compress WAV files, and it can
accommodate files with multiple channels, at sampling rates from 6 to
192 KHz, and at 8-,16-, 24-, and 32-bit resolution. The compression
rate ranges from 30 percent to 70 percent, depending on the source file.

The WavPack encoder offers options for both lossless and lossy
compression as well as a ``hybrid'' mode, which creates a lossy
compressed file and a second ``correction'' file that can be used to
restore the compressed file to its original lossless state. The encoder
is available in versions for Windows, Linux, and Mac OS X. All versions
are run from a command line, but an optional Windows interface is
available.\footnote{Most of this information is taken from the WavPack
site: David Bryant, ``WavPack Audio Compression,''
 \url{http://www.wavpack.com}  (Accessed 14 December 2005).}

\subsection{Proprietary Formats}

The three major proprietary formats---Windows Media, RealAudio, and
QuickTime---now offer lossless codecs for use with archiving as well as
streaming. The usual caveats related to proprietary formats apply here
as well: the sponsoring companies may offer encoding software, and their
popular media players (Windows Media Player, RealPlayer, Quicktime
Player) may be able to play back the files, but if the sponsoring
company were to discontinue support for the format, users would likely
be left to rely on legacy software.

\subsubsection{Monkey's Audio (extension \texttt{.ape})}

Monkey's audio was developed by Matthew T. Ashland ``for fun to keep
myself busy during the cold Minnesota winter.''\footnote{Response to the
question ``Could you tell me about the future of Monkey's Audio?'' in the
FAQ contained in version 3.99 of the Monkey's Audio software (Accessed
13 December 2005).} The Monkey's Audio encoder can encode mono and
stereo WAV files at resolutions of 8, 16, or 24 bits and at any sampling
rate. According to Ashland, the program has been optimized for use with
compact-disc audio (stereo, 16-bit resolution, 44.1 KHz sampling). It
achieves compression rates of about 40 to 50 percent. ID3 tags are
supported, but third-party tagging programs are required to use the more
expansive ID3v2 tags.

The current Monkey's Audio (version 3.99) is available only for the
Windows platform, although the official website mentions that versions
for Apple and Linux are in development.\footnote{See
 \url{http://www.monkeysaudio.com}.} Although Monkey's Audio is not an
open-source project, use of the encoder and the format are free for
personal or educational purposes; permission must be granted by the
author for commercial use.

\section{``Lossy'' Compression}\label{lossy}

The most common compressed audio formats use ``psychoacoustic models''
to discard audio data that cannot be heard or that is typically ignored
by the human ear. By eliminating this data, a file can be reduced in
size while minimizing the effect on the sound. These formats that
selectively discard data are known as lossy formats, and they can
produce files that are anywhere from one-fourth to one-thirtieth the
size of the original uncompressed audio, with a corresponding
degradation in fidelity.

\subsection{MPEG}

Among the lossy formats, those based on MPEG standards are the most
popular. MPEG is a suite of open standards for compressed audio and
video developed by the Motion Picture Experts Group, a working group
established in 1988 under the direction of the International Standards
Organization.

MPEG's standards have been released in families, each
designated by number. MPEG-1 (approved in 1992), supports video encoding
as well as mono and stereo audio encoding at three sampling rates;
MPEG-2 (1994) increases the number of sampling rates and provides for
broadcast-quality video and surround sound; MPEG-4 (1998) supports a
broad range of multimedia and is able to integrate synthetic audio
systems (such as MIDI and text-to-speech programs); MPEG-7 (2001)
provides tools for managing metadata.\footnote{The numbering scheme for MPEG is not strictly sequential; there is 
no MPEG-3, -5, or �6.}

Of the many formats provided by the MPEG standards, the most common are
MP3 and AAC.

\subsubsection{MP3 (extension \texttt{.mp3})}

MP3, officially known  as MPEG-1 Audio Layer III, is  an audio subset of
the 1992 MPEG-1 standard. (Layer  III also received some enhancements in
the MPEG-2  standard.) MP3  files were front  and center in  the digital
music revolution  of the 1990s  and gained notoriety through  their open
sharing on peer-to-peer networks.

The MP3 format has been particularly popular because it can produce
``near CD'' quality\footnote{``Near CD'' quality is entirely subjective
and can vary depending on the listener. For some, compressed audio
encoded at 128 kbps might be nearly indistinguishable from a CD; for
more sophisticated listeners, the rate needs to be pushed up to 196
kpbs.} audio at a compression rate of 11 to 1. In other words, one
minute of compact-disc audio, which requires about 10 MB of storage, can
be compressed to an MP3 file smaller than 1 MB. Despite the development
of compression formats that produce better sound quality at identical
bitrates---such as AAC and Ogg Vorbis---MP3 remains the most popular
audio format on the internet, and it has become the lingua franca of
personal digital audio players.

Although the specifications of the MPEG standards are open and freely
available, the Fraunhofer Institute and Thompson Multimedia---the
companies that helped finance the development of the standards---hold
patents on many of the algorithms used to code and decode MPEG
files.\footnote{For information the Frauenhofer Institute's and
Thomson's patent claims, see Gabriel Bouvigne, ``Patents and MP3,''
 \url{http://www.mp3-tech.org/patents.html}  (Accessed 10 December
2005). Thomson's licensing information is available at
 \url{http://www.mp3licensing.com}  (Accessed 10 December 2005).} In 1998,
when the Fraunhofer Institute issued a letter stating that it would
begin charging royalties to developers of MP3 encoders, some
distributors removed MP3 codecs from players, and some developers
decided to begin work on truly open formats, such as Ogg Vorbis (see
below).

\subsubsection{Advanced Audio Coding (AAC)  (extensions \texttt{.aac}, \texttt{.mp4}, \texttt{.m4a}, etc.)}\label{aac}

Advanced Audio Coding (AAC) was developed under MPEG-2 and enhanced
under MPEG-4. In the MPEG family of standards, AAC is the heir apparent
to MP3. Until the introduction of AAC, MPEG audio formats were
``backward compatible,'' which means that files created with earlier
standards could be played with decoders for the newer standards. With
the introduction of AAC, MPEG abandoned backward compatibility in order
to take advantage of newer coding algorithms and took the practical
precaution of assigning it a name that would distinguish it from its
``MP'' predecessors.\footnote{David Austerberry, \emph{The Technology of
Video and Audio Streaming,} 2nd ed. (Burlington, MA: Focal Press, 2005),
122. The MPEG-4 variety of AAC has been confusingly referred to as MP4,
which reinforces the perception of AAC as the successor to MP3 while
mixing apples with oranges: the ``3'' in ``MP3'' refers to Layer 3 in
the MPEG family of standards, but there is no Layer 4 that would
correspond to ``MP4''; in this case, the ``4'' refers to the MPEG-4
group of standards, which provides for much more than AAC.}

AAC provides better sound quality than MP3---particularly at lower bit
rates---and it supports sampling rates from 8 kHz to 96 kHz, compared to
MP3's 16 kHz to 48 kHz. One claim to fame for the MPEG-4 AAC format was
its adoption by Apple as the basis for the audio format used by its
iTunes music store.\footnote{The AAC audio purchased on Apple's iTunes
store is contained in files in Apple's proprietary \texttt{.m4p} format, which
includes a digital rights management wrapper that controls use of the
file.} In fact, because of the close association of AAC with the iPod,
it is often mistakenly assumed that AAC stands for ``Apple Audio
Codec.''

Files with the extension \texttt{.aac} are MPEG-2 AAC files; only a few
audio players are able to support these files. AAC audio data is more
frequently contained in an MPEG-4 file (similar in structure to a
QuickTime file), which is supported by most popular audio players. A
number of confusing file extensions are applied to MPEG-4 files, and
their interpretation can be challenging. Although the official MPEG-4
file extension is \texttt{.mp4}, this extension is not found as
frequently as the ones applied by Apple for use with the iPod and
iTunes: \texttt{.m4a} (``MPEG-4 audio'') is used for files ripped using
iTunes, \texttt{.m4p} (``MPEG-4 protected'') is used for files purchased
on the iTunes Music Store (the ``protected'' refers to embedded digital
rights management), \texttt{.m4b} (``MPEG-4 bookmarkable'') is used for
audio book files that can be ``bookmarked,'' and \texttt{.m4v} (``MPEG-4
video'') is used for audio/video files.\footnote{``MP4,''
 \url{http://www.audiocoding.com/modules/wiki/?page=mp4}  (Accessed 3
February 2006)}

Although AAC is a part of the open MPEG standards, the situation with
licensing is similar to the one with MP3: the patent rights to the
codecs used with AAC are held privately---in this case by AT\&T, Dolby,
the Fraunhofer Institute, and Sony---and developers who incorporate AAC
codecs into their software must pay royalties to the patent holders.\footnote{Fries \& Fries, 170.}

\subsection{Proprietary Formats}

\subsubsection{Windows Media Audio (extensions \texttt{.wma} and \texttt{.asf})}

Windows Media Audio (WMA) was introduced by Microsoft in 1999 as a
competitor to MP3, and while it was slow to catch on at first, its
popularity has increased in recent years. Several online music
stores---including Napster---use WMA (with Digital Rights Management) as
the basis of their service, and a growing number of portable digital
players support the format. WMA files are usually wrapped in an Advanced
Systems Format (ASF) file, a fully documented format that provides
streaming capability.

Microsoft's Windows Media offerings include an encoder (Windows
Media Encoder), various software development kits, and a player (Windows
Media Player). There are both lossy and lossless codecs available for
WMA.


\subsubsection{RealAudio (extensions \texttt{.ram} and \texttt{.ra})}

The earliest live audio offerings on the web were radio broadcasts
streamed using RealAudio, introduced by Progressive Networks (now
RealNetworks) in 1995. This new format---and technology---led to the
rapid growth of streaming audio and video webcasts during the late
1990s. With the subsequent development of competing formats,
RealAudio's market share has deteriorated, but it is still a
popular choice for streaming radio broadcasts, and it is still the
format of choice for streaming digital audio reserves in music
libraries. One advantage of RealAudio is the support of SMIL files,
which allow a series of audio files to be played consecutively without
prompting from the user. This feature is particularly useful with longer
works, such as operas and multi-movement works, which are typically
divided into multiple tracks on compact disc recordings.

RealNetworks applications in support of RealAudio include a player
(RealPlayer), encoder (RealProducer), and streaming server
(RealServer). In July 2002, RealNetworks launched Helix, an open-source
initiative that builds on programming code released by the company. The
Helix Community currently offers a player (Helix Player), encoder (Helix
Producer), and server (Helix Server), all of which are developed to
support RealAudio.

\subsubsection{QuickTime (extension \texttt{.mov})}

QuickTime, developed by Apple Computer, is a popular format for
streaming video and multimedia presentations encoded in various
formats. The first version was released in December 1991, and Apple
initially used QuickTime to provide video, graphics, and audio content
on CD-ROMs. It remains the most popular format for CD-ROM video. In
fact, Apple was fairly late in offering streaming capability for
QuickTime, which was not made available until the release of Version 4
in June 1999---four years after the introduction of RealAudio.

The QuickTime is a ``container'' format that is particularly useful for
synchronizing the content of numerous multimedia files, which may be
stored in different locations. The process of editing a multimedia
presentation in QuickTime is much simpler than in other formats, and
because of this facility, MPEG adopted the QuickTime \texttt{.mov}
format as the basis for MPEG-4 in 1998. In an odd twist, Apple held off
on incorporating the resulting MPEG-4 standard into QuickTime following
a dispute with the MPEG-4 license holders over licensing fees. The two
parties reached a compromise, and QuickTime 6 was released in July
2002. As of this writing, the latest release is Version 7.0.3.

\subsection{Open Format}

\subsubsection{Ogg Vorbis (extension \texttt{.ogg})}\label{ogg}

Ogg Vorbis is a free and open audio format developed and maintained by
Xiph.org.\footnote{Xiph.org was originally named Xiphophorus, which explains the 
choice of a fish as the official logo for Ogg Vorbis. 
 \url{http://www.streamingmediaworld.com/audio/tools/vorbis}   (Accessed 
13 December 2005).} Chris Montgomery began the Ogg Vorbis project at the
Massachusetts Institute of Technology soon after the Fraunhofer
Institute announced in September 1998 that it would begin charging
licensing fees for use of the MP3 format.

It is a fairly new format; the specifications were established in May
2000. Strictly speaking, Ogg is a file format and Vorbis is an audio
format. Ogg can be used as a container for audio in other Xiph.org
formats (such as FLAC), and Vorbis can exist as raw data without the Ogg
container. Nonetheless, the audio format is commonly referred to as
simply Ogg Vorbis.

The quality of Vorbis audio at a given bitrate is comparable to AAC and
superior to MP3 and Windows Media Audio. At this point, though, the
format is not in wide use, perhaps because the patent owners MP3 and AAC
codecs have not been aggressive in collecting royalty payments for their
use.

\subsubsection{AIFC (extension \texttt{.aifc})}

AIFC or AIFF-C (Audio Interchange File Format Extension for Compression)
is a version of the AIFF format that accommodates compressed data. The
codec can achieve compression rates as high as 83 percent.

\chapter{Delivery to the Listener}

% {RG-need intro}

\section{Accessing Digital Audio Files}

Throughout most of the history of recorded sound, the traditional method
for distributing and accessing recordings has been a physical object---a
cylinder, a disc, a reel of tape, a cassette. During the first two
decades following the introduction of digital audio technology, this
tradition continued with the development of several physical formats for
digital audio data: the compact disc, digital audio tape, and the
minidisc.

Digital audio technology is quickly moving away from traditional
physical distribution to network distribution. Although network
distribution has been available for well over a decade, it was only with
the introduction of digital audio players in 1998 and Napster in 1999
that digital audio files were commonly distributed over networks without
the use of physical media, other than the hard drive of the destination
computer. Most industry observers predict that physical distribution of
sound recordings will eventually be abandoned altogether.

In this section, we will look at the four most common ways that digital
audio files are distributed from one computer to another over networks:
making them available on servers for downloading, streaming them in real
time, sharing them over peer-to-peer networks, and syndicating them as a
podcasts.

\subsection{Downloading (by John Anderies)}

To download is to transfer the content of a digital file from a remote
computer and store a copy on a local computer. The remote computer is
usually called a server, and the destination computer is called a client
workstation. The file is usually transferred via protocols such as HTTP
(Hyper Text Transfer Protocol) or FTP (File Transfer Protocol). The
amount of time required to download a sound file depends on several
factors: the size of the file, the amount of bandwidth available for the
transfer, and to some degree, the performance of the client workstation
itself.

In the simplest instance, a sound file must be completely transferred
and saved to the client workstation before playback may begin. A newer
method, called ``progressive downloading,'' allows playback to start
before the sound file is completely transferred to the client
workstation. Under the right conditions, this can mean almost
instantaneous playback, and for that reason the end result of
progressive downloading is not unlike the next delivery method we'll
consider: streaming.

\subsection{Streaming}\label{streaming}

Unlike the process of downloading, which transfers whole files to the
client workstation, streaming divides the file into small packets of
data, which are sent in a continuous stream to the client workstation,
which discards the packets after playing them.

Streaming technology evolved in the mid-1990s when network and dial-up
speeds increased, computer audio technology became commonplace on
desktop computers, and audio compression formats made it possible to
reduce the data content of audio files while maintaining an acceptable
level of audio quality. Initially, streaming technology was most
commonly used to deliver radio broadcasts in real time over the
internet. In the mid-1990s, academic libraries recognized the potential
of streaming technology to improve the delivery of listening assignments
to students, and by 1996, several libraries were digitizing listening
assignments and making them available through streaming servers.

Streaming technology offers several advantages over downloading for
distributing audio over a network. Digital audio files can be very large
(roughly one megabyte of data for every minute of compressed audio
encoded at 128 kbps),\footnote{The exact figure is .9155 MB. For a
formula to calculate the size of a compressed audio file, see p.
\pageref{formula}} and depending on the speed of the network connection,
downloading one minute of compressed digital audio can take anywhere
from a few seconds to several minutes. Streaming audio allows the user
to listen without having to download the entire file. When a user
requests an audio stream, the streaming server begins sending packets of
data to a buffer---a digital holding tank---on the client workstation,
and a second or two later, once the small buffer is filled, the player
can start playing. Also, because the player works with only a small part
of the file at a time and discards it once it has been played, streaming
audio technology discourages illegal copying and distribution of
copyrighted material, since the entire sound file is never stored on the
listener's computer.

Using streaming audio for listening assignments offers several
advantages over traditional delivery methods. Streaming audio technology
allows library users to listen to recordings on any computer connected
to the internet, and with wireless access points in libraries, in
airports, in coffee shops, in hotels, listening can be done practically
anywhere. Also, in the past, because only a few people could listen to a
sound recording at a time, students often had to wait in line for an
assigned recording to become available, even when the library made
multiple copies. Streaming audio allows an entire class of students to
listen to the same selection at the same time.

\subsection{Peer-to-Peer (P2P) networks}

Downloading and streaming are client--server technologies. Both involve a
central ``server'' that stores the audio data and delivers it to a
software ``client'' running on a user's computer. With a
client--server system, the data is under the complete control of the
central server; the server controls what is distributed and who is able
to access it. This central control in the client--server model is a
strength as well as a weakness. The clients are dependent on the single
server's ability to handle all of the requests it receives for
data. If the server is overwhelmed---or is down completely---no content
can be delivered.

Peer-to-peer networks (often abbreviated ``P2P'') avoid dependence on a
central server by spreading the responsibility for delivering content
across the individual computers on the network. Each computer acts as a
server, and the data moves laterally from peer to peer. Once an audio
file has been downloaded to a computer, that computer can then make the
file available for sharing with others. A peer-to-peer network draws on
the computing power, bandwidth, and content of the individual computers
participating in the network. If one computer is down, there is no
noticeable degradation of service because the remaining computers on the
network are available to fill the void.

Peer-to-peer networks are informal. All that is needed to participate is
the appropriate software application, and computers join and leave the
network on a whim. The number of computers sharing content changes
minute by minute, so content available one day might not be available
the next. The participants on the network are usually not known to each
other, and they are traceable only by their network address.

The informal, amorphous nature of peer-to-peer networks make them a
convenient vehicle for anonymous filesharing, and they have gained
notoriety for enabling the illegal sharing of copyprotected sound
recordings, videos, and films. Most of the files shared on peer-to-peer
networks are copies of commercial content being distributed without the
permission of the owner, and for that reason these networks have become
targets for litigation by the recording and film industries. Librarians
are advised not to tap into the commercial audio resources available on
these networks. The networks, however, are also a rich source for
nonprofessional bootleg recordings and unreleased outtakes.  By no means
is all of the content on P2P networks being shared illegally, but
caution is advised.

The first popular peer-to-peer network was Napster, established in June
1999 by Shawn Fanning, who wrote the underlying program while a student
at Northeastern University in Boston.\footnote{Strictly speaking,
Napster was not a pure peer-to-peer network, since it relied on central
servers to maintain lists of connected systems and the files they made
available for sharing. This also opened it up to successful
litigation. More recent peer-to-peer networks have abandoned this
central-server model.} Napster became especially popular with college
students, who were able to take advantage of fast broadband campus
networks for speedy, efficient filesharing. In December 1999, the
recording industry, alarmed that tens of thousands of copyprotected
files were being shared free of charge through Napster, pursued legal
action against the company, and a March 2001 injunction shut down
Napster as a free file-sharing service.\footnote{The Napster brand and
logo were acquired by Roxio in 2002 for use with a commercial service
released in October 2003, but beyond the name, the commercial Napster
bears no resemblance to the original file-sharing platform.}

The recording industry's ongoing attempts to shut down companies that
develop and distribute filesharing programs has led to a game of cat and
mouse; as soon as Napster was gone, filesharers moved to other
platforms, and despite aggressive legal action by the recording
industry---not only against the developers of peer-to-peer software but
against individual filesharers---their popularity continues unabated. As
of the end of 2005, the four most popular peer-to-peer filesharing
networks are eDonkey, BitTorrent, FastTrack, and Gnutella, and each
network can be accessed through a number of software clients.

Filesharing accounts for the majority of data traffic on the internet,
and since 2005, movies and videos have surpassed music as the most
popular content shared. A 2005 study of global internet traffic by
CacheLogic showed that 60 percent of all internet traffic is the product
of filesharing, and of the files shared on the four major platforms, 62
percent were video and only 11 were audio.\footnote{Jason Meserve, ``P2P
Traffic Still Dominates the 'Net,'' Networkworld, 29 August 2005, 16.}

Although peer-to-peer networks have little---if any---application in a
library setting, they have been of great interest to the library
community for the intellectual property challenges they have raised. In
fact, most of the litigation involving digital audio and video has
centered on attempts to curb filesharing. In 2005, the Supreme Court
ruled unanimously that Grokster (the developer of software used with the
FastTrack network) could be held liable for users' copyright
infringements.\footnote{Case no. 04-0480, 545 U.S.\_\_\_\_ (2005).} The future of music distribution will undoubtedly be
shaped by such legal decisions as they are handed down.

\subsection{Podcasting (by John Anderies)}

Podcasting is essentially the same as downloading, but with the added
element of syndication technology, which delivers the sound file to the
client workstation automatically as part of a subscription.

Syndication protocols (such as RSS and Atom) allow users to subscribe to
weblogs and other online content. The subscriptions are known as
``feeds,'' and they are read by using a news- or feed-reader. At
particular intervals, the reader makes a call to the server that
provides the feed to see if there is new content that can be
retrieved. If so, it is automatically downloaded to the client
workstation.

In the case of weblogs, the content of a feed is usually text-based;
podcasts are the audio equivalent---an audio feed. Because these audio
files are often loaded onto iPods and other MP3 players for listening
once they have been downloaded, the process has been termed podcasting.

Podcasting technology allows inexpensive, quick, and easy distribution
of audio content. Because the audio is downloaded to the client
workstation, however, most podcasts consist of noncommercial
content---spoken commentary, movie reviews, travelogues, idle
observations on life---and steer clear of musical content because of
intellectual property issues. Several universities are now using podcast
technology as a means of distributing lectures and other noncommercial
course-related audio content through an Apple project called iTunes U.

\section{Software for Playback}

A key component to any digital audio service is the audio player---a
software program used to play back digital audio, either as a stream or
as a downloaded file. Depending on the type of audio service you
provide, the decisions you will need to make about players will range
from the simple to the fairly complex.

The developers of the common proprietary audio formats (Microsoft, Real,
and Apple) provide players designed specifically to play back those
audio files. While these players---like the audio formats---are
proprietary, they are distributed free of charge to users in order to
promote both the audio format and the player. In some cases, a basic,
stripped-down version of the player is offered at no cost, and a
``premium'' version with added features is available for a charge. These
features may include, for example, the ability to rip and burn compact
discs.

Often the choice of player will depend on what type of audio files you
plan to stream. Many of the proprietary players will not play sound
files in formats supported by competitors. For example, Windows Media
Player will not currently play protected AAC (iTunes) files, and the
iTunes player will not currently play Windows Media Audio. If all of
your digital audio is encoded in the same format, then it makes some
sense to use the proprietary player associated with that format. On the
other hand, if you offer audio in multiple formats, you must either
provide multiple players or identify a single player that can handle all
of the relevant formats.

For most libraries, there are two broad categories of listeners to
digital audio services: those in-house who rely on library workstations
for listening and those who use their own computers---either in-house or
remotely---to access the service. The software requirements for the
workstations used by these two categories of listener are different: an
in-house listening station simply needs players that are compatible with
whatever operating system and browser are used on public
workstations. Often systems staff will include audio players as part of
a standard public workstation ``disc image,'' and the only ongoing
responsibility of the music librarian is to make sure the players
continue to function whenever the browser software and the operating
system are upgraded.

The situation is not so simple when providing service to remote users,
who will prefer to access the service with their chosen operating
system, browser, and audio player. In order to provide the best service
to the largest number of users, you should run tests on computers
running both Windows and MacOS to determine which software
configurations are compatible with your service. (Linux users are used
to being neglected and often derive some satisfaction from discovering
workarounds on their own.  And they'll tell you about them.) Of course,
it would be impossible to test all permutations of operating systems,
browsers, and players, but you should be able to recommend at least one
successful combination of browser and player for both Windows and
MacOS. Be sure to provide your users with a detailed list of systems
requirements for your service---complete with web links to the pages
where players and browsers can be downloaded---and update it regularly.

\subsection{Common Audio Players}

There are dozens of computer applications that play back digital
audio---far more than could be covered sufficiently in this book---so I
will highlight four freely distributed proprietary players that are
often used with digital audio projects as well as one open-source player
that is a good alternative choice for libraries that offer digital sound
in multiple formats.

To test the capabilities of the players, I took sample files in five
formats---MP3, RealAudio, Windows Media Audio, AAC (in both an MPEG-2
and an MPEG-4 format file), and Ogg Vorbis---and attempted to play them
on the latest version of each player, as it is, ``out of the box,''
without importing additional
codecs. The table in figure~\ref{fig:capabilities} summarizes the
results.\footnote{The WAVE, FLAC, MP3, AAC, WMA, and Ogg files were
created using Easy CD-DA Extractor, and the RealAudio file was created
using RealProducer.}
 
\begin{figure}
\begin{tabular}
  {|c||c|c|c|c|c|c|c|c}
\hline            & WAVE & FLAC & MP3 & RealAudio & WMA & AAC & Vorbis \\
\hline\hline WMP        & Yes  & No   & Yes & No        & Yes & No  & No \\
\hline RealPlayer & Yes  & No   & Yes & Yes       & Yes & Yes & No \\
\hline QuickTime  & Yes  & No   & Yes & No        & No  & Yes & No \\
\hline iTunes     & No   & No   & Yes & No        & No  & Yes & No \\
\hline VLC        & Yes  & Yes  & Yes & Yes       & Yes & Yes & Yes\\
\hline
\end{tabular}
\caption{Capabilities of five common audio players} \label{fig:capabilities}

\end{figure}

From this table, it would be easy to conclude that MP3 is the ideal
format (since it can be played by all the players) and VLC the ideal
player (since it can play all the formats), but the situation is a bit
more complicated than that. Other formats provide better fidelity than
MP3 at similar bitrates,\footnote{See, for example, ``Advanced Audio
Coding'' and ''Ogg Vorbis'' on p.~\pageref{aac} and p.~\pageref{ogg}
above.} and the support community for VLC is far smaller than for the
proprietary players.

Many of the popular proprietary players---such as Windows Media Player,
RealPlayer, and QuickTime Player---are also designed to serve as media
content browsers to access news reports, videos, shopping sites, and so
forth. Like iTunes, they can also synchronize content with portable
digital players and connect directly to digital music stores, where use
licenses can be purchased for individual tracks. The latest version of
Windows Media Player and RealPlayer can also play DVDs. These extra
features add to the size of the application and the demands placed on
computer resources. Unless these added features are needed by your
users, they will be best served by a stripped down, freely distributed
``basic'' version of the player, which will load more quickly and
perform more reliably than the full-featured versions.

In this section, we will look only at the functionality of the players
for playing back audio. The use of other features of the players---such
as ripping CDs and encoding files---will be covered elsewhere.

\subsubsection{Windows Media Player}

Windows Media Player (WMP) is a proprietary player developed by
Microsoft that has been bundled with the Windows operating system since
the release of Windows 98 Second Edition in 1998. The player is also
available for independent download, but the most recent version, WMP 10
(released in September 2004), requires Windows XP and is not compatible
with earlier versions of Windows.

Although earlier versions of WMP were released for MacOS and Solaris,
there are no plans for future development of WMP for non-Windows
platforms. WMP 9 for Mac OS, released in 2003, was a disappointing
product that performed poorly. Microsoft now distributes a QuickTime
Player plugin, WMV Player, to support Windows Media on the Mac platform.

\emph{Audio formats supported:} for encoding: Windows Media Audio (48 to 192
kbps; variable bitrates also available), Windows Media Lossless, MP3
(128 to 320 kbps; requires installation of plugin); for playback: MP3,
Windows Media Audio (WMA) and other native Windows formats, such as
Windows Media Video (WMV) and Advanced Streaming Format (ASF).

\emph{URL for download:}  \url{http://www.microsoft.com/windows/
windowsmedia}  

\subsubsection{RealPlayer}

RealPlayer is a proprietary multimedia player developed by RealNetworks
to support its various RealMedia formats. The first version, released in
April 1995 (under the name ``RealAudio Player''), was one of the
earliest players to support streaming audio, and RealPlayer remains one
of the oldest audio players with an ongoing history of
development. There are full-featured versions of the player for Windows
that play back DVDs, download tracks to portable digital players, rip
and burn CDs, and provide an iTunes-like catalog of audio tracks as well
as an integrated web browser,. RealNetworks charges a fee for the
full-featured versions of the player. For simple playback of audio and
video, however, there are free ``basic'' versions that are better suited
for a library setting. This basic player is available in versions for
Windows, MacOS, Linux (and other versions of Unix), as well as several
handheld and mobile devices. The Helix community also offers a basic
player, known as Helix Player.

RealNetworks maintains an archive of ``legacy'' versions of the player,
which is valuable to users searching for an audio player that is
compatible with older versions of Windows and Mac OS.

\emph{Audio formats supported:} for encoding: WAV, MP3 (32 to 320 kbps;
variable bitrate also available), RealAudio (32 to 320 kbps), RealAudio
lossless, MPEG-4 AAC (96 to 320 kbps), and WMA (64 to 192 kbps); for
playback: MP3, RealAudio (including RealAudio lossless), WMA, AAC.

\emph{URL for download:} \url{http://www.real.com}; Real Legacy Software
Archive: \url{http://forms.real.com/real/player/blackjack.html}; Helix
Player: \url{http://player.helixcommunity.org}

\subsubsection{QuickTime Player}

Apple's QuickTime Player is designed to play QuickTime audio and video
files. For many years, the player has also been licensed to developers
for use with QuickTime files in third-party software applications. Apple
itself uses the QuickTime Player as the playback engine for its iTunes
software.

\emph{Audio formats supported:} MP3, AAC in an MPEG-4 (or QuickTime) file, AAC
encoded with FairPlay (\texttt{.m4p} files from the iTunes Music Store), Apple
Lossless.

\emph{URL for download:}
 \url{http://www.apple.com/quicktime/download/standalone.html}. (Caveat:
 the default download site for QuickTime Player
 (\url{http://www.apple.com/quicktime/download}) offers the player
 bundled with iTunes.)

\subsubsection{iTunes}

When iTunes for MacOS was released in January 2001 (a Windows version
would follow in October 2003), it set new standards for convenience and
usability in personal music management software. The program was
developed by Apple to serve many purposes. For a typical user, the chief
application of iTunes is to manage the content of an iPod, but iTunes is
also an independent media player, rich with features. The program can be
used to organize playlists, rip compact discs, encode audio, burn CD-R
copies, download podcasts, listen to internet radio stations, and
purchase music through the integrated iTunes Music Store. A distinct
disadvantage of iTunes as a player, however, is that files must be
incorporated into an iTunes playlist before they can be played back; it
is not possible simply to open a file and play it. The player itself is
based on the QuickTime Player, and the two are most frequently bundled
together for download.

\emph{Audio formats supported:} for encoding: WAV, AIFF, MP3 (16 to 320 kbps;
variable bitrates also available), AAC (16 to 320 kbps; variable
bitrates also available), Apple Lossless; for playback, MP3, MPEG-4 AAC
(.m4a), AAC encoded with FairPlay (.m4p files from the iTunes Music
Store), Apple Lossless. Will play back WMA files only after converting
them to MPEG-4 AAC.

\emph{URL for download:}  \url{http://www.apple.com/itunes/download} (includes
QuickTime Player)

\subsubsection{VLC}

VLC is an open-source media player with versions for Windows, Mac, and
various Linux distributions, and it is the only player that could play
back all seven of the sample audio files (see
fig.~\ref{fig:capabilities} on p.~\pageref{fig:capabilities}). It is a
relatively small program and requires little CPU power, unlike some of
the large, feature-rich media players. Although it is not nearly as
popular as the four players just covered, I include it to show that
there are alternatives to the proprietary players, which often include
features that are not needed for simply playback of audio content.

\emph{Audio formats supported:} WAV, FLAC, MP3, RealAudio (using the Cook codec), Windows Media Audio, AAC, Vorbis.

\emph{URL for download:}  \url{http://www.videolan.org/vlc} 


\chapter{Hardware and Software to Support Digital Audio}

This section covers the computer hardware, audio components, and software typically used in a digital audio projects. 

\section{Equipment}

The choice of equipment for a digital audio project will vary depending
on the recording formats you are working with and the amount of
modification you want to make to the sound signal. A modest
course-reserve encoding project based only on compact disc recordings
can be put in place with nothing more than a laptop, while a full-blown
audio preservation project that includes 78s, LPs, and tapes will
require professional-quality audio components to play back the sound as
well as additional components to process the audio signal.

Because of the fundamental difference between digital and analog
recordings, different processes are used to convert each to digital
audio files.\footnote{For a description of the differences between
analog and digital recordings, see ``Analog and Digital Sound'' on
p.~\pageref{ads} above.}  A digital recording---such as a compact
disc---already consists of digital audio data, so the process involves
simply reading the digital data on the disc and storing it as a file on
a computer. This conversion can be done by any computer with a CD-ROM
drive that is running CD extraction (or ``ripping'') software. The time
needed to extract the audio from a CD will vary according to the speed
and throughput of your computer's CD-ROM drive and microprocessor, but
because the computer is processing data and not sound, extracting CD
audio always takes considerably less time than playing back the audio in
real time.

Analog recordings must first be converted into digital data before being
stored as a file on a computer. This work is done by a digital audio
converter (DAC), which is a component part of the computer's sound card
or, optionally, its external digital audio interface.\footnote{For more
detailed information on the digitization of sound, see ``Fundamentals of
Digital Audio'' on page \pageref{fundamentals} above.} The analog recording
is played back on a traditional audio component---typically a turntable
or tape deck---whose output is patched into an amplifier or
preamplifier, which in turn is patched into the computer's sound card or
audio interface.

The source audio can be modified by additional components and software
either during the creation of the digital audio file or afterwards. Some
common types of manipulation include eliminating stretches of silence at
either end of the recording, adjusting the equalization to boost or
suppress certain frequency ranges, or filtering out tape hiss, surface
pops on a recording, and other extraneous noises.

\subsection{Encoding workstation}

An appropriately equipped computer workstation is the single essential
piece of equipment for a digital audio project. The quality of the
uncompressed audio created from analog sources and the efficiency of its
encoding will be dependent on the capabilities and performance of this
central component. When selecting a computer for encoding, the most
important features to consider are the microprocessor (speed and bit
capacity), memory (size and speed), hard disk (capacity and
performance), CD-ROM/DVD drive (speed), and sound card or audio
interface (bitdepth and sampling rate).

The specifications of computer workstations are constantly
improving. Over increasingly shorter intervals of time, microprocessors
double in speed, memory doubles in size, and hard drives double in
capacity, while workstations decrease in price. The technology for
external storage is also rapidly changing; over the past few years we
have moved from recordable CD-ROMs to recordable DVDs and external hard
drives to small USB flash-memory drives.

Because the technology is developing so quickly, it would be misleading
to suggest specifications for a digital audio workstation, since any
recommendation would be outdated as soon as it is made. You can feel
confident, though, that when selecting a workstation, you will never
regret investing extra money to purchase a faster processor, more
memory, or a larger hard drive.

Other specifications for the workstation are ultimately less important,
but they also happen to be hotly contested. The operating system, for
example: Apple or Microsoft---or even Linux? About one quarter of the
survey respondents report that they are using Macs for their digital
audio project, with the remainder presumably using Windows.\footnote{No
one reported using the Linux operating system on their workstation, but
software does exist to support a digital audio project using Linux. In
fact, in 2001 the author launched a successful digital audio reserves
project at the University of Illinois using a Linux workstation for
encoding.} Each has its ardent partisans, and although historically the
Mac has had an edge over the Windows platform in the development of
hardware and software for multimedia, at this point the platforms
perform equally. There is no convincing technological reason to choose
one over the other, so your decision should be guided by your choice of
software, since all audio programs are not available in versions for
both platforms. If you have no preference for software, then stick with
whichever platform is already established in your library, or the one
you're most familiar with.

For Windows computers, which microprocessor is best, Intel or AMD? Both
perform acceptably well. The factors to consider are compatibility and
price. Intel has set the standard for PC microprocessors since the
introduction of the IBM PC in the early 1980s. Because Intel chips are
an industry benchmark, developers of operating systems, software, and
computer peripherals make sure their products are compatible with Intel
microprocessors. AMD, on the other hand, manufactures microprocessors
that perform as well as Intel's and meet their specifications
but at much lower prices. The decision between Intel and AMD can mean a
difference of several hundred dollars in the cost of a
computer. Although Intel is perceived to be the safer choice,
there's no good reason not to purchase a computer with a
cheaper AMD chip.

If your digital audio project is small in scale, and your budget will
not allow the purchase of a dedicated workstation, you can easily mount
a digital audio project using a workstation that is shared with other
applications. There are advantages, however, to devoting a workstation
exclusively to digital audio. When a computer is shared with other
applications, it can easily become cluttered with programs and multiple
processes running in the background, which will degrade the general
performance of the machine. You will find that even a computer fresh out
of the box will have several programs running in the background by
default.\footnote{If you don't know how to find these and disable them
yourself, ask someone in your systems office to review these background
processes with you to make sure that only essential ones are running.}

Thirty-one of the respondents to our survey reported on the equipment
they use for their digital audio project. Of these, five (16\%) are
digitizing only compact discs, and two of these are doing the work on a
laptop. Most libraries devote a single computer to encoding; only three
respondents (about 10\%) reported that their encoding workstation is
shared with other applications.

\subsubsection{Sound card or audio interface}

Every computer manufactured today is equipped to record and play back
sound. Sound capabilities are provided by a soundcard, either integrated
into the computer's circuitry or installed as a separate
component plugged into a slot on the motherboard. Typically, this
preinstalled sound card, however, is of mediocre quality, intended
simply to play back system sounds and music for recreational listening.

If you are digitizing analog recordings (LPs and cassette or
reel-to-reel tapes), the quality of audio your workstation can produce
will be greatly improved through an upgrade to the sound card supplied
with the computer. Until a few years ago, this meant installing or
replacing a card inside the computer. With the introduction of Firewall
and USB2, the most convenient way to upgrade your computer's sound
system is to purchase an audio interface, a stand-alone component that
plugs into the computer's Firewall or USB2 port. Also, an independent,
external audio interface can easily be moved from one computer to
another, which simplifies upgrading and replacing the encoding
workstation.

Audio interfaces range widely in features, functionality, and cost. Some
of the more popular manufacturers are M-Audio, Edirol, Tascam, and Mark
of the Unicorn (MOTU). A few years ago, a typical stock sound card
installed in a computer offered 16-bit resolution and a 48 kHz sampling
rate. As use of digital audio technology has grown, audio interface
technology has become more sophisticated, offering deeper resolution
(24-bit is now standard) and faster sampling rates (up to 192
kHz). Three survey respondents offered information on the specific brand
and model of the audio interface used for their project, and in all
cases, the interface offered 24-bit resolution and a sampling rate of up
to 96 kHz.\footnote{An argument can be made that there is no reason for
the sampling rate ever to exceed the 44.1 kHz rate of CD audio because
of the 20 kHz limit to human hearing and the Nyquist Theorem's formula
for sampling at twice the rate of the highest frequency to be
reproduced.  Sampling above 44.1 kHz certainly produces higher-quality
audio, but the enhanced quality cannot be perceived by the human ear.}
Some studio-quality audio interfaces offer 32-bit resolution, and
inevitably the technology will continue to advance over time.

\subsection{Audio components}

\subsubsection{Playback}

A digital audio project drawing exclusively on a compact disc collection
requires no equipment other than a computer with a CD-ROM drive. Most
libraries, however, are digitizing analog recordings as well as compact
discs, and these formats require additional components to play back the
recordings. The components are usually patched into a mixer or
amplifier, which in turn is patched directly into the computer's sound
card or audio interface. To work with tape recordings, components are
added that are appropriate for playback of tape through a traditional
sound system---for example, a cassette, reel-to-reel, or DAT deck.

The quality of sound that can be reproduced from older analog recordings
will depend on the condition of the recording and the quality of the
component playing it. Libraries that have been providing listening
services for several decades will have turntables and tape decks that
are probably, at this point, underused and can be co-opted for the
digital audio project.

The high-quality playback that is essential to preservation work can be
provided only by high-end components, and some are designed with
preservation in mind. A laser turntable, for example, allows playback of
an LP or 78 without contact with the disc, so repeated playback results
in no wear whatsoever.

The equipment configuration used for most digital audio projects
consists of a computer with a CD-ROM drive, a turntable, a cassette
deck, and an amplifier.\footnote{For more information on audio
components, see Jim Farrington, \emph{Audio and Video Equipment Basics
for Libraries,} Music Library Association Basic Manual Series, no. 5
(Lanham, MD: Scarecrow Press, 2006).} The analog recording format most
frequently digitized by libraries is the LP. Eighteen (58 percent) of
the thirty-one survey respondents have a turntable devoted to their
digital audio project. Next in frequency, with fifteen (48 percent) is
the cassette deck. After that, the numbers fall off sharply. Three
libraries use DAT decks, and two use reel-to-reel decks.

Some compact discs cannot be read by a computer's CD-ROM
drive. This is most often occurs with older compact discs. These discs
must be played on a traditional compact-disc player, which is patched
into the system as if it were a turntable or tape deck. Two of the
survey respondents have independent CD players devoted to their digital
audio projects.

\subsubsection{Mixer}

If your digital audio project draws on a number of audio components for
sound audio, then you will benefit from adding a small mixer, a
scaled-down version of the large mixing boards seen in recording
studios. A mixer allows you to switch smoothly between multiple input
sources without removing and replacing cables. An amplifier can provide
the same functionality, but typically an amplifier can accommodate no
more than three or four input sources. A eight-input or sixteen-input
mixer should fill the needs of most digital audio projects.

Each input of a basic mixer has jacks to receive the input signal and a
dial or slider called a potentiometer (or ``pot''). The pot is used to
control the volume of each input and allows the user to fade a source in
or out. For example, if you typically include a spoken announcement or
description at the beginning of an audio-reserve selection, the mixer's
potentiometers will allow you to make a seamless transition from the
announcement to the music by turning down the volume of the microphone
after the announcement while turning up the volume of the turntable or
other audio component. More sophisticated mixers have input sensitivity
controls, filters, equalizers, and other features.

A mixer also provides multiple outputs. One output will be routed to
your computer's soundcard or audio interface. You may choose
to have another output routed to an amplifier equipped with speakers so
that you can cue up sound recordings and play back the audio you have
created on something other than the small speakers supplied with most
computers. Mixers also have a headphone jack so that you can monitor
exactly what is being output by the mixer.

\subsubsection{Other components}

Libraries that are digitizing for preservation may use disc-cleaning
machines, filters, noise-reduction modules, and equalizers.

% [Some of the components used by respondents to our survey include:
% mixer, independent amplifier/receiver, audio interface, noise reduction
% module, equalizer, preamp.]

\subsubsection{Input types}

A sound card or audio interface usually has two types of input jacks:
low signal and high signal. The low-signal input is used for microphones
and other devices that produce a weak signal requiring amplification by
the sound card. The jack is usually marked ``mic in'' and is often
colored red.

The high-signal input is used for electronic components, such as tape
decks, DVD players, VCRs, amplifiers, receivers, and mixers. A number of
different labels are used for the high-signal input. Some of the most
common are ``aux in'', ``line in,'' or ``audio in.'' 

A turntable is one of the few audio components that uses a low-signal
input, but turntables are usually routed into into a preamplifier or
amplifier rather than directly into the sound card. The preamplifier or
amplifier, in turn, would be plugged into a mixer or directly into the
high-signal input jack.  

% and is often colored [?blue].

It is important not to confuse the low- and high-signal inputs. An
electronic component plugged into the sensitive low-signal input will
overpower it and produce distorted sound. On the other hand, a
microphone plugged into the high-signal input will be barely audible.

\subsection{Servers}

A server is a computer that provides services on request to computers on
a network. The services are often related to shared resources---such as
printers, data files, media files, web pages---and the server is
expected to provide them at any time, day or night.

In most library settings, the installation and maintenance of servers is
under the purview of an information technology department, either in the
library or at a broader institutional level, and rare is the case where
a librarian is expected to maintain a server.

All network-based digital audio projects, however, rely on services
provided by servers, so anyone managing digital audio project should
have a basic understanding of what servers are, how they differ from
desktop computers, and what kind of software they run to provide
streaming audio services.

\subsubsection{Servers compared to desktop workstations}

A computer used as a server contains many of the same components as a
desktop workstation---a microprocessor, memory, a hard drive, a network
connection. In fact, a standard-issue desktop computer is equipped to
provide the functionality of a server, and for small applications that
deliver modest services to a few users, a desktop computer can
simultaneously fill the dual roles of desktop workstation and server. A
computer intended to act as a server works most efficiently, however,
when it is dedicated solely to server tasks and its hardware is
optimized for performance as a server.

Since most of the work of a server is related to delivering data,
computers designed for use as servers are equipped with high-performance
hard drives and network interfaces that deliver data far more quickly
than a standard desktop computer. Also, very little processing power is
required to deliver data, so servers have no need for the powerful
microprocessors required by desktop computers to manipulate and display
data. Because commands are issued to servers remotely from other
computers, there is no need for a video card, monitor, keyboard, or
other external peripherals. A typical server consists of a standalone
box or a component mounted on a rack.

\subsubsection{Operating systems}

Like desktop computers, servers can run a variety of operating systems,
and systems specialists enjoy debating the relative merits of each. The
most common are Unix (in its many flavors, most notably FreeBSD,
Solaris, and Linux---which itself comes in many flavors), Microsoft's
Windows Server System, and Apple's OS X Server. Unlike the world of
desktop computers, where Microsoft dominates, among server operating
systems, Unix traditionally has been the major player. In fact, Unix is
most common operating system for web servers by a wide margin, although
Microsoft recently been making gains.\footnote{According to a February
2006 survey of more than 76 million websites at 
 \url{http://news.netcraft.com/archives/web\_server\_survey.html}, the
Apache web server (a Unix application) was used by 67 percent of the
sites, while Microsoft's server was used by 21 percent.}

The choice of operating system is driven partly by the server
hardware. Microsoft and Unix operating systems run on Intel-based
processors (Unix can also run on several other classes of processor),
and Apple's operating system runs on Apple servers.

The choice of operating system is usually transparent to the user of a
server, and one should function as well as another. Some information
technology departments, however, have rigid preferences for certain
operating systems and hardware, and when planning a digital audio
project, you might be expected to work with whatever server operating
system happens to be supported. Smaller information technology
departments, in particular, will be resistant to adopting a new server
platform to support a single project.

This becomes an issue when planning a digital audio project, because the
choice of operating system will, in turn, define the possible choices
for the software that will drive the digital audio service.

\subsubsection{Software for delivering audio}

For digital audio projects, servers provide two basic functions: storing
audio files and delivering them to users. There are several ways a
server may deliver digital audio to a client. The two most common are
(1) using a web server to make a digital audio file available for
downloading and (2) using a streaming server to deliver a stream of
digital audio data to a digital audio player.

The first option is the easiest, since web servers are ubiquitous, and
the question becomes simply one of storage space. When a user keys the
appropriate URL into a browser or clicks a link to the URL on a web
page, the web server delivers the file to the browser, and once the file
is transferred completely, it can either be played back or stored on the
local computer. Some audio formats---such as Microsoft's Advanced
Streaming Format (ASF)---provide ``progressive playback,'' which allows
playback of a file to begin before it is fully downloaded.\footnote{As
we mentioned above, though (see ``Streaming,'' p.~\pageref{streaming}),
using download technology to deliver copy-protected audio exposes you to
the risk of legal action. Be sure to check with your institution's legal
department before setting up a listening service that allows users to
download and save copies of copy-protected audio.}

Delivering audio as a stream requires a streaming server, which is
simply a server running streaming software. If your institution already
maintains a streaming server, you might investigate the possibility of
adding your digital audio service to the existing server. In fact, most
digital audio projects end up sharing a streaming server with other
streaming media projects. Seventy-nine percent of the respondents to our
survey reported that their service shares a server with other
applications.

As mentioned earlier, the choice of server operating system can dictate
the choice of streaming server software, which will in turn dictate the
type of audio files you can deliver through your service. According to
our survey, the two most popular streaming servers are RealNetwork's
Helix Server (along with its predecessor, RealServer) and Apple's
QuickTime Streaming Server.  The Helix Server software is available for
the Windows 2003 Server, Linux, and Solaris operating systems, and the
server can deliver files in RealAudio, Windows Media, Quicktime, MP3,
and AAC formats. The QuickTime Streaming Server software runs on Apple's
OS X and can stream audio contained in QuickTime (\texttt{.mov}) files
as well as AAC (\texttt{.mp4}) files.

Some smaller libraries have even set up a digital audio service by
ripping CD tracks in iTunes and making the resulting library available
on the library's network.

\section{Software (by John Anderies)}\label{software}

\subsubsection{Audacity}

Audacity is a free, open-source digital audio editor that runs on
the Mac, Windows, or Linux operating systems. It allows the user to play,
record, and edit sound files including the WAV and Ogg Vorbis
formats. With the addition of a plugin called the LAME MP3 Encoder,
Audacity will handle the MP3 format as well. Audacity does not have the
built in capacity to rip compact discs but is an excellent tool for
converting analog audio to digital audio, as well as for manipulating
the digital file once it is created. 

% Effect such as… sampling rates…

\subsubsection{iTunes}

In addition to being an online audio player, storage system, and music
store, iTunes may be used as a digital-audio editor too. Developed by
Apple Computer, iTunes is available free for download and is compatible
with both Mac and Windows operating systems. iTunes can play back a
variety of file formats including AAC, AIFF, MP3, MPEG-4, and WAV.
However, it is limited to ripping compact discs and converting digital
audio from one format to another.  

% [mention of its MP3 converter, problems]

\subsubsection{QuickTime Pro}

Like iTunes, QuickTime Pro was developed by Apple Computer and is
compatible with both Mac and Windows operating systems. QuickTime Pro is
available for purchase and includes a number of features that its free
relation (QuickTime) does not include. QuickTime Pro may be used to
convert and compress digital audio in a variety of formats including
AIFF, MPEG-4, and WAV.  

% [does this need more?]

\subsubsection{RealProducer}

RealProducer Basic and RealProducer Plus are proprietary products of
RealNetworks that convert digital audio in a range of file formats
(including AIFF, AVI, MP3, MPEG-4, and QuickTime) into compressed
RealAudio files (\texttt{.ra}, \texttt{.ram}, \texttt{.rm}) for
distribution through RealServer or Helix Server. RealProducer Basic is free,
while RealProducer Plus is available for purchase. Both run on the
Windows and Linux operating systems only. RealProducer Plus includes
features such as unlimited target audiences/bitrate streams and batch
processing.

\subsubsection{Sound Forge}

Sound Forge is a digital audio editing and creation tool produced by
Sony Media Software (formerly produced by Sonic Foundry) and available
for purchase. It is compatible with the Windows operating system
only. Sound Forge will rip compact discs as well as convert analog audio
to digital audio. It offers a full suite of audio editing tools and can
export files in AIFF, MP3, Ogg Vorbis, RealAudio, WAV, and WMA formats.


\part{Digital Audio in the Library}

\chapter{Sources for Digital Audio Recordings}

%\section{Commercial Services}
%
%\subsection {Subscription services}
%
%Services that offer a library of recorded sound for a flat subscription fee. (Arranged here in alphabetical order; a logic-based order would be better...)

%\subsubsection{Classical Music Library}
%
%\subsubsection{Database of Recorded American Music (DRAM)}
%\subsubsection{Napster}
%
%The case of Penn State.
%
%\subsubsection{Naxos Music Library}
%\subsubsection{Smithsonian Global Sound}
%
%\subsection{Per-track Leasing}
%
%
%(Is there a better term to use for this type of service?) What services
%are still out there besides iTunes?

%\subsubsection{iTunes Music Store}
%
%\subsubsection{Rhapsody}

\section{Digitizing Library Local Collections}

Early in the days of digital library projects, we read quite a bit about
the prospect of entire research libraries being digitized; some writers
were so bold as to predict a date. In these early days, it was assumed
that libraries---either singly or cooperatively---would take on the
responsibility for the digitization of library collections. During the
past decade, however, commercial enterprises have taken the lead in the
digitization of print content, and recording companies have been
entering into licensing agreements with various online services for the
delivery of commercial sound recordings over the internet.

As library digitization projects have become more numerous and more
sophisticated, libraries have moved beyond the idealistic (and
ultimately impractical) goal of digitizing ``everything'' to the more
realistic goal of digitizing only content that is rare and in some cases
unique---content outside the scope of commercial digitization
enterprises, content that highlights the materials that distinguish one
library different from another. Focusing on special collections not only
brings unique content to the public; it also provides a promotional tool
that can showcase a library and its host institution.

Most music libraries own such collections of unique, noncommercial sound
recordings. For a college or university library, these might be
recordings of concerts, recitals, and lectures that have taken place on
campus, or field recordings made by a researcher and donated to the
library. For a public library, it might be recordings of local community
musical groups or guest lectures.

Because these recordings are unique, they are also irreplaceable, so
most libraries have imposed restrictions on their use in order to
protect them. Digitizing these special recordings and making them
available digitally accomplishes two goals: the recordings are more
easily accessible---available to all listeners, both inside and outside
the library---and they are preserved. Once the sound recording has been
digitized, there is no further need to use the original recording, so
the original sound recording can be stored permanently and is protected
from any damage it might receive through use.

% American Memory
%
% An excellent example an audio digitization project based on unique local
% content is the ``American Memory'' site prepared by the Library of
% Congress. It's a free site that offers a digital record---in
% words, images, and sound---of ``American history and creativity.''

% University of California, Santa Barbara

\chapter{Curricular Listening}

In academic libraries, the sound recordings that are used most heavily
are usually those assigned by instructors for course-related listening
by students. In larger universities, music appreciation and music
history survey courses often have enrollments of hundreds of students
spread over several sections. The puzzle of how best to deliver
listening assignments to large groups of students simultaneously has
been dogging music librarians for decades.

Some instructors will require students to purchase a set of recordings
that accompany the assigned text for the course, in which case the
library is relieved of the responsibility. In most cases, though, the
instructor will prepare a listening list that is tailored to suit his or
her preferences for repertory and performances. 

When supporting a customized listening list, the library cannot
accommodate the needs of a large class---particularly on the night
before an exam---by simply placing the library's copy of the various
recordings on the reserve shelf.  Through the years, music libraries
have turned to state-of-the-art audio technologies for solutions to the
problem of providing an effective reserve listening service for heavily
enrolled classes. 

In the 1970s and 1980s, reserve listening was provided by copying LP
recordings to reel-to-reel or cassette tapes in multiple copies for
students to borrow. (Some libraries piped the recordings from a central
tape player to multiple listening carrels in a listening center.) In the
1990s, with the advent of recordable compact discs, this same technique
was transferred to the new technology; libraries burned circulating
copies of the listening assignments on CD-Rs.

In the mid-1990s, many libraries quickly adopted new streaming-audio
technology to provide reserve listening over the internet, and today, a
growing number of libraries are making use of commercial subscription
services (such as Classical Music Library and Naxos Music Library) and
digital music players (such as iPods) to provide reserve listening
assignments.

% In this section, we will look at two popular applications of digital
% audio technology for the delivery of reserve listening: streaming audio
% and portable digital music players.

In order to learn more about current practices in music libraries, I
posted a note on MLA-L,\footnote{\texttt{mla-l@listserv.indiana.edu};
archives available at  \url{http://listserv.indiana.edu}.} the email
discussion list of the Music Library Association, calling for volunteers
to fill out a survey that asked questions about software, hardware,
access, and staffing for the digital audio services offered in their
libraries. Forty-two librarians responded to the survey, and while the
survey is by no means scientific, it was the best method I had to
identify current practices in the field. So before proceeding, I offer
this caveat: when I refer to ``most libraries,'' ``few libraries,'' or
``no libraries,'' I am drawing conclusions based on practices in the
forty-two libraries represented in the survey results.

\section{Streaming Service}

The earliest widespread application of digital audio technology was in
the mid-1990s, when several music libraries began providing streaming
audio for recordings placed on reserve for course assignments. The focus
on curricular listening assignments was a natural choice, since reserve
recordings are heavily used and usually constitute a comparatively
small, well-defined collection.

Streaming technology is still the most popular means of providing
network delivery of reserve listening. It allows libraries to provide
around-the-clock reserve listening both on campus and off, and students
appreciate the convenience of being able to whenever and wherever they
please.

\subsection{Creating and Managing the Sound Files}

The most time-intensive activities in providing a streaming-audio
reserves service are encoding, describing, organizing, and preserving
the digital sound files. There are a number of ways to approach these
tasks, and careful thought and planning will pay off once your project
is in production.

\subsection{Encoding}

A crucial step in planning a streaming audio project is selecting the
format and bitrate for the compressed audio files that will be streamed
to users. The quality of the audio produced for your project will be
affected by your choices, since some formats produce higher-quality
sound than others at identical bitrates. The bitrate will affect the
performance of your service, since streaming audio at higher bitrates
require greater bandwidth and faster internet connections.

When selecting a format for your streaming digital audio project, the
factors that are likely to have the greatest impact on your decision are
the ones that, in the end, will probably be invisible to you: the
streaming server and the staff in charge of maintaining it. If your
project is to be hosted on an existing media server maintained by
personnel outside your departmental library, you will probably be
expected to work within the limitations of that server, in which case
certain decisions will already have been made for you.

A factor of less concern in selecting a streaming audio format is sound
quality; all compressed formats, at a sufficient bitrate, will deliver
acceptable audio to users. Keep in mind, though, that newer
formats---such as AAC and Ogg Vorbis---produce audio of higher quality
than older formats---MP3, for example---at an identical bitrate.

The choice of bitrate for the audio files will determine not only the
quality of sound but the minimal connection speed for your service. Most
users now access the internet using fast broadband
connections---ethernet, cable, or DSL---and these can easily handle
streams of 128 kbps. If you know that a significant number of your users
connect to the internet using slower modem connections, you might
consider encoding at two different rates (perhaps 48 kbps and 128 kbps)
or use a format (such as RealAudio's Surestream) that can
accommodate streams at multiple rates. It is clear, however, that the
days of slow, dial-up modems are numbered, so it is better to err on the
side of higher bitrates if you want to extend the usability of your
compressed files.

Another factor to keep in mind when selecting a streaming audio format
is your users' preferences for operating systems. Media players exist
for most streaming formats in versions for Windows, MacOS, and Linux, so
most streaming services will be compatible with all three operating
systems. RealAudio and the MPEG-based formats, because they have a long
history and are well established, are safe choices if you want to be
sure that your service is accessible on all platforms. On the other
hand, if your library uses Macs for public workstations and most of your
users own Macs, then selecting format tailored for Windows (such as
Windows Media Audio) would be a poor choice. If a strong preference for
a specific operating system exists at your institution, then it will
probably influence the choice of the streaming server, and the
capabilities of the server will, in turn, influence your choice of a
streaming audio format.

In the end, a successful streaming audio service can be based on any
common compression format. Your decision should be made in
reverse. Start by talking with the staff who will manage the streaming
server that will host the service. They will tell you which formats are
compatible with the server. Once you have a short list of possible
formats, try playing audio streams in each format off the
web.\footnote{Radio stations are an excellent source for testing the
compatibility of various audio streams. The Public Radio Fan site
(\url{http://www.publicradiofan.com}), for example, indexes stations
according to a number of criteria, including streaming format.} If you
want to support multiple players or operating systems, be sure to try
the streams using every possible combination and take note of whether
software or plugins need to be installed to playback the stream.  This
should give you some idea of what will be required of your users to
configure their systems to play back streams in each format.  Finally,
consider the quality of the audio.

The survey revealed that most libraries use one of two formats for their
streaming audio: MP3 (47 percent of the respondents) and RealAudio (39
percent of the respondents). Use of Quicktime (presumably AAC files in a
QuickTime wrapper) was reported by 11 percent of the respondents. Also,
some of the libraries that use the MP3 format specified that the files
are streamed in a QuickTime wrapper. One library (3 percent) bases its audio
service on Windows Media Audio.

\subsubsection{Naming and Organizing Files}

Over the course of a few semesters, even the smallest digital audio
reserve project can generate hundreds of audio files. Labeling and
organizing a large group of files presents special challenges that can
be approached in a number of ways. The two fundamental decisions to be
made are (1) how to assign names to the audio files and (2) how to
organize them into folders (or directories). It is best to settle on a
system for naming and organizing files before you start encoding. Try a
number of methods and test them on a small scale to predict how they
might work with your service. Fixing problems later, after you have
processed hundreds of files, will be difficult and costly, so this will
be time well spent.

From the survey of forty-two libraries providing digital audio services,
I learned that there are nearly as many ways to name and organize
digital audio files as there are libraries providing digital audio
services. Although few libraries use identical methods, all use a
combination of data elements drawn from the same five categories of
data. Each category has certain advantages and disadvantages.

\paragraph{Musical content}

\begin{description}

\item \emph{Typical data elements:} composer's last name, title of
composition, title of component part(s) of composition, performer

\item \emph{Advantages:} Content of the audio files can be easily identified

\item \emph{Disadvantages:} Often requires a long string of characters in order to
produce a unique file or folder name; names and titles must be
standardized (authority control); the source recording can be identified
only by searching the catalog

\end{description}

\paragraph{Container (the physical sound recording)}

\begin{description}

\item \emph{Typical data elements:} label name, label number, disc number, track number

\item \emph{Advantages:} Unique file and folder names can be easily constructed;
source recording can be quickly identified

\item \emph{Disadvantages:} Requires a search of file metadata or the library catalog
to determine the content

\end{description}

\paragraph{Shelving number (used for filenames only)}

\begin{description}

\item \emph{Typical data elements:} call number or accession number used for shelving
in the local collection

\item \emph{Advantages:} Produces short filenames that are easily constructed; the
source recording can be retrieved quickly

\item \emph{Disadvantages:} Requires a search of file metadata, a catalog search, or
retrieval of the item to determine content of the audio file

\end{description}

\paragraph{Bibliographic record number (used for filenames only)}

\begin{description}

\item \emph{Typical data elements:} local bibliographic record number, bibliographic
utility (OCLC, RLIN) record number

\item \emph{Advantages:} Short, unique filenames that are easily constructed and
efficiently searched in the local catalog

\item \emph{Disadvantages:} Requires a search file metadata or a catalog search to
determine content

\end{description}

\paragraph{Curricular function}

\begin{description}

\item \emph{Typical data elements:} year/semester, course name, course
number, instructor

\item \emph{Advantages:} Easy management of files and folders by course
and instructor; file and folder names can be directly related to the
instructor's course syllabus

\item \emph{Disadvantages:} Data elements change from semester to
semester; multiple copies of file must be created when more than one
course uses the same track; requires a search of file metadata to
determine content

\end{description}

A filename should fill two functions: to provide a unique, concise
identifier for the file that will distinguish it from all other files,
and to provide information that will allow staff to determine the
content of the file and its source. In some ways, these two functions are
at cross purposes: data that does the best job of providing short,
unique filenames (bibliographic record numbers, for example) require
database searches to reveal a file's content; data that does
the best job of describing the file's content (composer,
title, label, label number) often produces long, unwieldy filenames.

Looking over the current practices in the libraries represented by the
survey, files are most often named by using data either based on the
musical content, shelving number, or bibliographic record number. Using
these elements allows files to be used for different courses and reused
from semester to semester. Few libraries construct filenames based on
the curricular function of the file. Here are some examples of how
librarians have approached the naming and organization of sound files,
taken from responses to our survey:


\texttt{MUS101/Puccini-Tosca-Sabata-EMI-1953-01-Ah\_Finalmente} [In
folders by course number; individual tracks named using composer last
name, work title, conductor, label, label number, disc number, track title]

\texttt{2005FA/MEN3335/dahl\_concerto\_mvt1} [In folders by year and
semester, then course number; files named using composer last name,
title, movement]

\texttt{Music240/00000000-02-11} [In folders by course number;
individual tracks named using OCLC number, disc number, track number]

\texttt{muen/275/bach\_cpe\_magnificat\_magnificat\_anima\_4211482} [In
  folders by course, number; files named using composer last name and
  first name, work title, component part, label number]

\texttt{MozartSym41i} [Composer, short title, movement]

\texttt{cd1234.2\_3} [File name using accession number, disc number, and
track number]

\texttt{Blue-Ridge-Ramblers.Jug-Rag.CD12134-2-1} [File name using
performer name, track title, accession number, disc number, track
number]

\texttt{Schumann-Dichterliebe-07-Ich grolle nicht} [File name using
composer last name, work title, track number, title of component part]

\texttt{cd-26504\_05} [File name using accession number, track number]

When naming a file based on its musical content, you can select the data
using a number of sources. The most reliable source would be the
appropriate MARC fields in the recording's bibliographic
record---the 100, 240/245, 700 \$a \$t, etc.---so that the form of the
composer's name and the title of a work will be consistent
for all files. The process of looking up authorized headings can be time
consuming, however.

Some libraries rely instead on metadata supplied by large databases of
compact-disc data, such as Gracenote's CDDB and Freedb.\footnote{See
 \url{http://www.gracenote.com}  and  \url{http://www.freedb.org}.}
Because most encoding programs automatically query these databases for
metadata, information on composer, performer, album title, and track
titles can be imported automatically, eliminating the need for data
entry for all but the most obscure compact discs. Also, encoding
programs can often be configured to construct file and folder names
automatically, based on the metadata elements retrieved from CDDB or
Freedb. 

The disadvantage to these compact disc metadatabases is that the data is
contributed by users, and no standards of consistency are applied to the
data.  Also, CDDB metadata can include ``extended characters'' (letters
with umlauts and accents as well as other special characters). If you
are relying on CDDB data to name your files, be sure to test filenames
that include extended characters and punctuation before you move your
project into production. Some servers and audio players can process
these filenames without a problem, but others choke completely on the
extended characters and are unable to play the file. Often the encoding
program or player offers an option to strip out extended characters from
filenames and metadata. At least one librarian uses an external program
to convert the characters.

\subsubsection{Backup protection of content}

Any digital audio project, regardless how small, represents an
investment of time, and because the creation of digital audio from
analog sources like LPs and cassettes must be done in real time---a half
hour of music requires at least a half hour for encoding---a project
that relies heavily on analog sources requires a significant investment
in time.  Protecting this investment, on the other hand, requires little
time and expense, especially when compared to the work that would be
required to recreate the project.

The most time-intensive step in the encoding process is the creation of
the uncompressed audio file.  If this file is preserved, the time spent
creating it will not need to be lost in the event of a natural disaster,
the malicious vandalism of a hacker, or something more innocuous---like
the migration to a different format for audio streaming.

Compressed audio files, on the other hand, are often not backed up, for
two good reasons. First, the time required to recreate a compressed file
is relatively insignificant (so long as you have retained the source CD
or uncompressed audio file) and as microprocessors grow faster, that
time becomes increasingly negligible. Second, as network speeds increase
and compression technologies become more sophisticated, it is inevitable
that an audio project will eventually migrate to a new compression
format for delivery, in which case the compressed files will eventually
need to be recreated.

Judging from the responses to the survey, the majority of libraries do
not create and maintain independent archival copies of audio
files---compressed or uncompressed---for their digital audio-reserve
services. Less than one third of the libraries routinely archive the
source files. This does not mean that most libraries routinely destroy
source files once they have been used. Often they will reside on the
encoding computer, but no backup is kept beyond this initial copy, and
if a disaster were to strike the encoding computer, the work would be
lost.

Even libraries who do routinely maintain archival copies of uncompressed
files choose not to back up uncompressed files ripped from compact
discs. The compact discs themselves can serve as a backup, and if the
compressed files created from a particular CD are lost---or need to be
recreated in at a different bitrate or in a different format---the
collection's copy of the source CD can be put into service. Because
replacement files can be digitized from a compact disc at a rate much
faster than real time, backing up uncompressed source files for compact
discs becomes a practice that consumes time and storage space when very
little risk is being assumed.

When backing up data, regardless of the medium, it is important to keep
the backup copies separate---physically and virtually---from the data
being protected. There are three back up methods reported in the survey:

\begin{description}

\item \emph{Remote server.} Files are copied to a remote server, which
  itself is routinely backed up by IT personnel. This method is simple
  and quick, since it places the bulk of responsibility on the
  administrator of the server, and the library simply needs to make sure
  that files are copied to the server as soon as they are created.

\item \emph{Recordable discs.} Files are copied to recordable compact
  discs (CD-Rs) or recordable DVDs. This method has the advantage of
  keeping the archival copies easily accessible and under the full
  control of the library, but it also requires the library to maintain a
  regular back up schedule and devise a routine for organizing and
  storing the CD-Rs.

\item \emph{External hard drive.} Files are copied to an external hard
drive, typically a USB drive that can attached easily to the computer
for backup and then removed for storage in a safe place.  The advantages
are ease and speed of the backup; the disadvantage is relying on a
storage device that itself might be subject to failure.

\end{description}

With backups, redundancy is important.  Better to set up two redundant
backup methods than to rely on one whose failure would spell disaster.

%Perhaps the ideal storage medium for archival backups is a server that
%itself is regularly backed up on a regular schedule, offering you, in
%effect, two layers of protection. Storing backups on a serit in a pl

%Lossless compression for backups of uncompressed files.

%Those libraries that do maintain separate archival copies typically use
%an external harddrive or the drive on a separate server.

%\subsection{Metadata}
%
%[administrative and structural; typical components; how it is used; embedding author, title, copyright information in soundfile; CDDB]

\subsection{User interface}

Of the thirty-four librarians who offered information on the interface
used for their digital audio reserves service, nineteen (56 percent)
report that links to the audio selections are provided through a course
management system, such as BlackBoard or WebCT. Seven (21 percent) use
independent web pages, six (18 percent) use their online catalog and/or
its reserve module.

Although none of the survey respondents report using Apple's
iTunes software, we know from distribution-list postings and reports at
conferences that some libraries provide listening assignments by
maintaining a network-accessible shared ``library'' on iTunes.

\subsection{Staffing}

The survey revealed that libraries have used a number of successful
staffing models for their audio reserves service. Most services are
launched with little or no increased staffing. Roughly three quarters of
the respondents were able to launch a digital audio reserves project by
redeploying existing staff out of necessity; it is often a decision
between adjusting job assignments of existing positions or not taking on
the project at all.

For those libraries that did receive an increase in support for the
project, the added staff ranged from one 20-hour per week student
assistant to 1 FTE support staff and five student assistants. In several
cases, the work for the project initially was absorbed by existing
staff, but once the project was established and grew in scope, a case
could be made with the libary administration for adding staff.

\subsubsection{Library's responsibilities}



For a digital audio reserves project, the library is almost always
responsible for encoding the audio, uploading it to the server, and
providing an interface for access.

Once a digital audio reserves project is up and running, most of the
ongoing work involves digitizing and encoding the source
recordings. Among the thirty-three respondents to the survey who
answered questions about staffing, twenty-five (76 percent) report
support staff are involved in digitization and encoding. Twenty-two
(67 percent) use student assistants, usually in combination with
support staff, although four libraries (12 percent) have only students
working on recordings. Thirteen (39 percent) reported that a librarian
is involved, and in four cases librarians do all of the digitization
and encoding work.

For preservation projects and large digital audio reserves projects, the
library may employee a full-time audio specialist to digitize and encode
the audio.

Back in the days of tape-based reserve services, the responsibility for
creating listening tapes rested with the instructor---or more commonly,
with the instructor's teaching assistant---and the library simply
handled the reproduction and circulation of the tapes. This model
continues at several institutions who replied to the survey. Teaching
faculty and staff create audio files for their listening lists and
sometimes also mount them on a central server or on the
course-management software site for their course. This is the exception
to the norm, though, and although some faculty and staff prefer to have
control over their curricular listening assignments, it is in the best
interest of the students and the institution to have curricular
listening services centralized to provide a uniform interface and
uniform quality and to make sure intellectual property laws are
observed.

\subsubsection{Systems staff responsibilities}

Systems staff are typically responsible for maintaining the server
hardware and the streaming software. Depending on how technology
support is shared in an institution, these staff might be employed by
the departmental library, the general library, or the campus IT
department.

%Of the thirty-two respondents to the survey who answered questions
%about staffing

%\section{Portable Players}
%
%iPod use for class listening; Examples from Duke, perhaps?
%
%\chapter{Preservation}
%
%[Using digital audio techniques to preserve analog sound recordings; the advantages it offers over traditional tape-based preservation]
%
%\section{Early formats}
%
%\subsection{Cylinders, 78s.}
%
%\subsection{Tape}
%
%\subsection{Reel-to-reel, cassette, etc.}
%
%\part{Looking toward the Future: Emerging Trends}
%
%[Ideas from  08 Nov 05 meeting]
%
%
%Continuing shift from ownership to access in the industry
%
%"Just in time"; where you want it when you want it.
%
%"Moving toward a mix of online audio services; commercial services
%blended with in-house digitization.
%
%Cooperative/consortial digitization projects for: (1) metadata and (2) content 
%
%ILL of sound files
%
%iPod successor: wireless audio device, the ultimate in untethered
%listening, and the ultimate in access vs ownership.

\appendix
\part{Appendix}
\chapter{Resources for Questions on Copyright}

When setting up a digital audio reserves service or any other service
that involves the delivery of copy-protected recordings over a network,
you should work with your institution's legal department to
insure that the proposed service is acceptable within their
interpretation of the Copyright Law. You may find that your
institution's legal services department will play a large role
in determining the content of your digital audio service and its
access. Institutional legal departments can vary greatly in how much
risk they are willing to allow their institution to assume. Some will
prohibit any services involving copy-protected recordings---even if
access is restricted. At the other extreme, there are institutions that
will allow instructors to rip CDs and upload MP3 files to a courseware
site for students to download to their iPods.  You are best advised to
clear your service with your legal department rather than to see it shut
down a few weeks into production.

As with any law, the copyright law can be read a number of ways,
depending on one's point of view and personal interests. In February
1996, the Music Library Association's Legislation Committee issued the
statement below, which supports the digitization of reserve materials
and their delivery over networks. The statement can be useful in
explaining to apprehensive library administrators how the law makes
provisions for digital audio reserves.

\begin{quotation}
\begin{center}\textbf{MLA's ``Statement on the Digital Transmission of
  Electronic Reserves''}\footnote{Music Library Association, ``Statement on the Digital
Transmission of Electronic Reserves,'' c1996-2002,
 \url{http://www.lib.jmu.edu/org/mla/guidelines/accepted\%20guidelines/Di
gital\%20Reserves.asp}  (Accessed 19 November 2005).}

\end{center}

Music educators cannot effectively teach the structure of a musical work
without providing aural access to the complete work. Attempting to
comprehend an entire musical composition through excerpts, or even
sections, is no more effective than attempting to comprehend a novel,
architectural plan, poem, or painting in the same manner. At best, only
a sense of style is conveyed, not compositional structure. Additionally,
educators who teach the history, culture, theory, composition, or
performance of music require the flexibility to select the compositions
they teach based on educational relevance and instructional
objectives. Recognition of the appropriateness of providing such
flexibility in instruction is expressed within Section 110 of the
copyright law, which states:

Notwithstanding the provisions of section 106, the following are not
infringements of copyright:

(1) performance or display of a work by instructors or pupils in the
    course of face-to-face teaching activities of a nonprofit
    educational institution, in a classroom or similar place devoted to
    instruction, unless, in the case of a motion picture or other
    audiovisual work, the performance, or the display of individual
    images, is given by means of a copy that was not lawfully made under
    this title, and that the person responsible for the performance knew
    or had reason to believe was not lawfully made;…


The American Library Association's ``Model Policy Concerning
College and University Photocopying for Classroom, Research and Library
Reserve Use'' (\emph{C\&RL News} [April 1982]: 127--131), as drafted by Mary
Hutchins, states the view that the library reserve room may be
considered an extension of the classroom. The Music Library Association
fully supports this view as well as the consequent view that students
enrolled in a class have the educational right to aurally access its
assigned musical works both in the classroom and through class
reserves. The MLA also believes that the dubbing or digital copying of
musical works for class reserves falls within the spirit of the fair use
provision of the copyright law.

In light of the above, the Music Library Association supports the
creation and transmission of digital audio file copies of copyrighted
recordings of musical works for course reserves purposes, under the
following conditions:

Access to such digital copies must be through library-controlled
equipment and campus-restricted networks.

Access to digital copies from outside of the campus should be limited to
individuals who have been authenticated: namely, students enrolled
either in a course or in formal independent study with an instructor in
the institution.

Digital copies should be made only of works that are being taught in the
course or study.

Digital copies may be made of whole movements or whole works.

Either the institution or the course instructor should own the original
that is used to make the digital file. The Library should make a good
faith effort to purchase a commercially available copy of anything that
is provided by the instructor.

The library should remove access to the files at the completion of the
course.

The library may store course files for future re-use. This includes the
digital copy made from an instructor's original if the library has made
a good faith effort to purchase its own copy commercially.

\end{quotation}

\section*{For Further Reading on Copyright}

The following citations are offered for reference when grappling with questions of copyright in the management of digital audio services.

\subsection*{U.S. Copyright Law}

\bc
Title 17 of the U.S. Code  \url{http://www.copyright.gov/title17}   (Accessed 18 November 2005).
\ec

\bc
Digital Millennium Copyright Act (H.R. 2281)  \url{http://lcweb.loc
.gov/copyright/legislation/hr2281.pdf}   (Accessed 18 November 2005).
\ec

\subsection*{Overviews}

\bc
Fries, Bruce, and Marty Fries. Digital Audio Essentials. Chapter 17,
``Digital Audio and Copyright Laws.'' Sebastopol, Calif.:
O'Reilly, 2005. \textsc{isbn} 0596008562. pp. 317--30.
\ec

{\small Offers ten hypothetical test cases to illustrate what practices are and are not acceptable under existing laws.}

\bc
Frith, Simon, and Lee Marshall, eds. Music and Copyright. 2nd ed. New
York: Routledge, 2004. \textsc{isbn} 0415972523.
\ec

\bc
Jeweler, Robin. ``Copyright Issues in Online Music Delivery.'' In John
V. Martin, ed., Copyright: Current Issues and Laws, 97-107.
\ec

\bc
Martin, John V., ed. \emph{Copyright: Current Issues and Laws.} New York: Nova
Science, 2002. \textsc{isbn} 1590332687.
\ec

\bc
Schrader, Dorothy. ``Digital Millennium Copyright Act, P.L. 105-304:
Summary and Analysis.'' In John V. Martin, ed., Copyright: Current
Issues and Laws, 131-52.
\ec

\bc
Vaidhyanathan, Siva. \emph{Copyrights and Copywrongs: The Rise of Intellectual
Property and How It Threatens Creativity.} New York: New York University
Press, 2001. \textsc{isbn} 0814788068.
\ec

\bc
Weimer, Douglas Reid. ``The Copyright Doctrine of Fair Use and the
Internet: Case Law.'' In John V. Martin, ed., Copyright: Current Issues
and Laws, 109-15.
\ec

\subsection*{Electronic Reserves}

\bc
American Library Association. Association of College \& Research
Libraries.  ``Statement on Fair Use and Electronic
Reserves.'' November 2003.  \url{http://www.ala.org/ala/acrl/acrlpubs/
whitepapers/statementfair.htm}   (Accessed 19 July 2006).
\ec

\bc
Music Library Association, ``Statement on the Digital Transmission of
Electronic Reserves,'' c1996-2002,  \url{http://www.lib.jmu
.edu/org/mla/guidelines/accepted%20guidelines/Digital%20Reserves.asp}  
(Accessed 19 November 2005).
\ec

\subsection*{Preservation}

\bc
Besek, June M. \emph{Copyright Issues Relevant to Digital Preservation
and Dissemination of Pre-1972 Commercial Sound Recordings by Libraries
and Archives.} CLIR Publication, no. 135.  Washington, DC: Council on
Library and Information Resources and Library of Congress,
2005. \textsc{isbn}
1932326235.  \url{http://www.clir.org/pubs/reports/pub135/contents.html} 
(Accessed 9 December 2005).
\ec

\bc
OCLC, Inc. ``Digitization \& Preservation Online Resource Center:
Copyright Online Copyright Resource Kit,''
 \url{http://digitalarchive.oclc.org/da/ViewObject.jsp?fileid=0000016179:000000676940\&reqid=1269}  
(Accessed 26 March 2006).
 \ec

\chapter{Glossary}

\begin{description}

\item [b] Bit

\item [B] Byte. 8 bits.

\item [Kb] Kilobit. 1,000 bits.

\item [KB] Kilobyte. Despite the ``kilo'' prefix, a kilobyte is not one thousand
bytes.  One kilobyte is 1,024 (2\^10) 8-bit bytes, or 8,192 bits.

\item [kbps] Kilobits per second.  A kilobit is 1,000 bits.

\item [kHz] Kilohertz. 1,000 cycles per second.

\item [Mb] Megabit. 1,000,000 bits.

\item [MB] Megabyte. 1,048,576 (220) bytes, or 1,024 kilobytes. It is
also 8,388,608 (1,048,576 * 8) bits, or 8,388.608 kilobits. Despite the
``mega'' prefix, a megabyte is not one million bytes.

\item [Mbps] Megabits per second.

\item [MHz] Megahertz. 1,000,000 cycles per second.  

\end{description}

\chapter{Bibliography}

\section*{General}


\bc 
Austerberry, David. \emph{The Technology of Video and Audio Streaming.} 2nd
  ed. Burlington, Mass.: Focal Press, 2005. \textsc{isbn} 0240805801.
\ec

\bc
Bailey, Andy. \emph{Network Technology for Digital Audio.} Boston: Focal Press,
  2001. \textsc{isbn} 0240515889.
\ec

\bc
Ballora, Mark. \emph{Essentials of Music Technology.} Upper Saddle River, N.J.:
  Prentice Hall, 2003. \textsc{isbn} 0130937479.
\ec

\bc
Edstrom, Brent. \emph{Musicianship in the Digital Age.} Boston: Thomson Course
Technology, 2006. \textsc{isbn} 1592009832.
\ec

\bc
Farrington, Jim. \emph{Audio and Video Equipment Basics for Libraries.} Music
Library Association Basic Manual Series, no. 5. Lanham, MD: Scarecrow
Press, 2006. \textsc{isbn} 0810857162.
\ec

\bc
Fries, Bruce, and Marty Fries. \emph{Digital Audio Essentials.} Sebastopol,
Calif.: O'Reilly, 2005. \textsc{isbn} 0596008562.
\ec

\bc
Middleton, Chris. \emph{The Complete Guide to Digital Audio: A Comprehensive
Introduction to Digital Sound and Music-Making.} Boston, MA: Muska \&
Lipman, 2003. \textsc{isbn} 1592001025.
\ec

\bc
Pohlmann, Ken C. \emph{Principles of Digital Audio.} 5th ed. New York:
McGraw-Hill, 2005. \textsc{isbn} 0071441565.
\ec

\bc
White, Glenn D., and Gary J. Louie. \emph{The Audio Dictionary.} 3rd
ed. Seattle: University of Washington Press, 2005. \textsc{isbn} 0295984988.
\ec

\section*{Digital audio formats}

\subsection*{General}

\bc
``Introduction to Digital Formats for Library of Congress Collections.''
 \url{http://www.digitalpreservation.gov/formats/intro/intro.shtml}.
\ec

\bc
Bosi, Marina, and Richard E. Goldberg. \emph{Introduction to Digital Audio
Coding and Standards.} Boston: Kluwer Academic, 2003. \textsc{isbn}
1402073577.
\ec
{\small Thorough, but highly technical, information on digital audio coding
algorithms and the MPEG family of standards. Treatment of psychoacoustic
modeling is particularly good. Provides no coverage, however, for
popular non-MPEG standards like WMA, Real, and Ogg Vorbis.}


\subsection*{FLAC}

\bc
Coalson, Josh. ``FLAC -- Free Lossless Audio Codec''
 \url{http://flac.sourceforge.net}   (Accessed 10 December 2005)
\ec

\subsection*{Monkey's Audio}

\bc
Ashland, Matthew T. ``Monkey's Audio: A Fast and Powerful Lossless Audio
Compressor.''  \url{http://www.monkeysaudio.com}  (Accessed 12 December
2005).
\ec

\subsection*{MPEG}

\bc
Fraunhofer IIS  \url{http://www.iis.fraunhofer.de/amm/techinf}   (Accessed 18 November 2005).
\ec

\bc
Moving Picture Experts Group. ``The MPEG Home Page.''  \url{http://www.chiariglione.org/mpeg}   (Accessed 18 November 2005).
\ec

\subsubsection*{AAC}

\bc
Fraunhofer IIS. ``Audio \& Multimedia: MPEG-2 AAC.''  \url{http://www.iis.fraunhofer.de/amm/techinf/aac}   (Accessed 18 November 2005).
\ec

\bc
Apple, Inc. ``QuickTime – Technologies – AAC
Audio.''  \url{http://www.apple.com/quicktime/technologies/aac}   (Accessed 9
December 2005).  
\ec

\subsubsection*{MP3}

\bc
Bouvigne, Gabriel. ``MP3-Tech''  \url{http://www.mp3-tech.org} 
(Accessed 10 December 2005).
\ec

\bc
---------. ``Patents and MP3''  \url{http://www.mp3licensing.com}  (Accessed 10 December 2005).
\ec

\bc
Fraunhofer IIS. ``Audio \& Multimedia: MPEG Audio Layer-3.''
 \url{http://www.iis.fraunhofer.de/amm/techinf/layer3}   (Accessed 18 November
2005).  Thomson, Inc. ``Mp3licensing.com – Home''
 \url{http://www.mp3licensing.com}   (Accessed 10 December 2005).
\ec

\subsection*{Ogg Vorbis}

\bc
Xiph.org. ``Ogg Vorbis Documentation''  \url{http://www.xiph.org/vorbis/doc}   (Accessed 10 December 2005).
\ec

\bc
Xiph.org. ``Vorbis Audio Compression''  \url{http://xiph.org/vorbis} 
(Accessed 13 December 2005).
\ec

\subsection*{Quicktime}

\bc
Apple, Inc. ``Quicktime.''  \url{http://developer.apple.com/quicktime} 
(Accessed 6 December 2005).
\ec

\subsection*{RealAudio}

\bc
RealNetworks, Inc. ``RealNetworks Documentation Library''  \url{http://service.real.com/help.library}  (Accessed 10 December 2005).
\ec

\subsection*{Windows Media}

\bc
Microsoft, Inc. ``Microsoft Windows Media.''  \url{http://www.microsoft.com/windows/windowsmedia}  (Accessed 6 December 2005).
\ec

\section*{Servers}

\subsection*{Operating Systems}

\subsubsection*{Apple}

\bc
Apple, Inc. ``Mac OS X Server''  \url{http://www.apple.com/server/macosx}  (Accessed 23 March 2006).
\ec

\subsubsection*{Linux}

\bc
FreeBSD Project. ``The FreeBSD Project.''  \url{http://www.freebsd.org} 
(Accessed 23 March 2006).
\ec

\bc
Red Hat, Inc. ``Red Hat: The Open Source Leader.''
 \url{http://www.redhat.com}  (Accessed 23 March 2006).
\ec

\bc
Sun Microsystems, Inc. ``Solaris Enterprise System.''
 \url{http://www.sun.com/software/solaris}  (Accessed 23 March 2006).
\ec

\subsubsection*{Windows}

\bc
Microsoft, Inc. ``Microsoft Windows Server System: Home.''
 \url{http://www.microsoft.com/windowsserversystem}   (Accessed 19 March 2006).
\ec

\subsection*{Streaming Server Software}

\subsubsection*{Helix}

\bc
RealNetworks, Inc. ``Products and Services    Media Servers.''  \url{http://www.realnetworks.com/products/media\_delivery.html}   (Accessed 19 March 2006).
\ec

\subsubsection*{QuickTime}

\bc
Apple, Inc. ``QuickTime -- Streaming Server.''  \url{http://www.apple.com/quicktime/streamingserver}   (Accessed 19 March 2006). 
\ec

\subsubsection*{Windows}

\bc
Microsoft, Inc. ``Windows Media Services 9 Series.''
 \url{http://www.microsoft.com/windows/windowsmedia/9series/server.aspx}  
(Accessed 19 March 2006).
\ec

\section*{Preservation}

\bc
Council on Library and Information Resources. \emph{Capturing Analog Sound for
Digital Preservation: Report of a Roundtable Discussion of Best
Practices for Transferring Analog Discs and Tapes.} CLIR Publication,
no. 137. Washington, DC: Council on Library and Information Resources;
Library of Congress, 2006. \textsc{isbn}
1932326251.  \url{http://www.clir.org/pubs/reports/pub137/pub137.pdf} 
(Accessed 13 April 2006).
\ec

\bc
Stanford University Libraries, Preservation Department, Conservation
Online. ``Audio Preservation.''  \url{http://palimpsest.stanford.edu/
bytopic/audio}   (Accessed 2 April 2006).
\ec

\bc
Rosen, Jody. ``How Pop Sounded before It Popped.'' \emph{New York
Times,} ``Arts and Leisure'' section, 19 March 2006.  On the University
of California, Santa Barbara, Cylinder Preservation and Digitization
Project.
\ec

\section*{Metadata}

\subsection*{ID3}

\bc
``ID3v2.''  \url{http://www.id3.org}   (Accessed 18 November 2005).
\ec

\section*{Peer-to-Peer Networks}

\bc
Katz, Mark. ``Living in Cyberspace.'' Chapter 8 of \emph{Capturing Sound.} (see
under ``Digital Audio and Culture'' below).
\ec

\bc
Merriden, Trevor. \emph{Irresistible Forces: The Business Legacy of Napster \&
the Growth of the Underground Internet.} Oxford: Capstone, 2001. \textsc{isbn}
1841121703.
\ec

\bc
Oram, Andrew, ed. \emph{Peer-to-Peer: Harnessing the Benefits of a
Disruptive Technology.} Sebastopol, CA: O'Reilly, 2001. \textsc{isbn} 059600110X.
\ec

\bc
United States Congress. House Committee on the Judiciary. Subcommittee
on Courts, the Internet, and Intellectual Property. ``Reducing
Peer-to-Peer (P2P) Piracy on University Campuses: A Progress Update.''
One Hundred Ninth Congress, First Session, 22 September 2005. Serial
no. 109-56  \url{http://purl.access.gpo.gov/GPO/LPS66466}  (Accessed 17
April 2006).
\ec

\section*{Subscription Services}

\bc
Quist, Ned., Darwin F. Scott, and Alec McLane. ``Naxos Music Library.''
\emph{Notes} 61, no. 2 (December 2004): 512--16.  
\ec

\section*{Portable Digital Audio Players}

\section*{Digital Audio in Libraries}

\bc Honan, Mathew. ``Libraries Turning to iPods and iTunes,''
\emph{Playlist,} 13 February 2006
 \url{http://playlistmag.com/features/2006/02/library} 
(Accessed 26 March 2006).  \ec

\bc
Lutz, Marilyn. ``The Maine Music Box: A Pilot Project to Create a
Digital Music Library.'' \emph{Library Hi Tech} 22, no. 3 (2004): 283--94.
\ec

\bc
Maple, Amanda, and Tona Henderson. ``Prelude to a Digital Music Library
at the Pennsylvania State University: Networking Audio for Academic
Library Users.'' \emph{Library Resources and Technical Services} 44, no. 4
(October 2000): 190--95.
\ec

\bc
Stewart, M. Claire, and H. Frank Cervone. ``Building a New
Infrastructure for Digital Media: Northwestern University Library.''
\emph{Information Technology and Libraries} 22, no. 2 (June 2003): 69--74.
\ec

\bc
Sullivan, Kathryn, John J. Stafford, and Cindy
Badilla-Melendez. ``Digital Music Project at Winona State University.''
\emph{Information Technology and Libraries} 23, no. 2 (June 2004): 70--73.
\ec

\bc
Walker, Diane Parr. ``Music in the Academic Library of Tomorrow.'' \emph{Notes}
59, no. 4 (June 2003): 817--27.  
\ec

\section*{Digital Audio and Culture}

\bc
Katz, Mark. \emph{Capturing Sound: How Technology Has Changed Music.} Berkeley:
University of California Press, 2004. \textsc{isbn} 0520241967.  See in
particular chapter 8, ``Listening in Cyberspace,'' which focuses on the
MP3/P2P phenomenon and intellectual property issues.
\ec

\bc
Lysloff, Rene T. A., and Leslie C. Gay. \emph{Music and
Technoculture.} Middletown, CT: Wesleyan University Press, 2003. \textsc{isbn}
081956513X.  
\ec

\section*{Digital Audio and the Recording Industry}

\bc
Barfe, Louis. \emph{Where Have All the Good Times Gone?: The Rise and Fall of
the Recording Industry.} London: Atlantic, 2004. \textsc{isbn} 1843540657.
\ec

\bc
Burkart, Patrick, and Tom McCourt. \emph{Digital Music Wars: Ownership and
Control of the Celestial Jukebox.} Critical Media Studies. Lanham: Rowman
\& Littlefield Publishers, 2006. \textsc{isbn} 0742536688.
\ec

\bc
Coleman, Mark. \emph{Playback: From the Victrola to MP3, 100 Years of
Music, Machines, and Money.} New York: Da Capo, 2003. \textsc{isbn} 0306809842.
\ec

\bc
Hull, Geoffrey P. \emph{The Recording Industry.} 2nd ed. New York:
Routledge, 2004. \textsc{isbn} 041596802X.  See in particular chapter 11, ``The
Recording Industry and the Internet.''
\ec

\bc
Katz, Mark. \emph{Capturing Sound: How Technology Has Changed Music.} Berkeley:
University of California Press, 2004. \textsc{isbn} 0520241967.
\ec

\bc
Kusek, David, and Gerd Leonhard. \emph{The Future of Music: Manifesto for the
Digital Music Revolution.} Edited by Susan Gedutis Lindsay. Boston:
Berklee Press, 2005. \textsc{isbn} 0876390599.  
\ec

\subsection*{Digital Rights Management (DRM)}

\bc
Howe, J. ``Licensed to Bill.'' \emph{Wired} 9, no. 10 (October 2001): 140--49.
\ec

\newpage

\begin{center}
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\end{center}

The typeface used for this document is Bitstream Charter, designed by
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\end{document}
