This dissertation explores tuning theories, concepts of sound, and their relation to cosmology in China between the mid-third century B.C.E. and the first century C.E. My overall argument is twofold: First, I argue that to truly understand musical thought in early China, we must realize that it was perceived as a technology. Sound and tuning, especially in a cosmological context, were often discussed in mathematical terms. Second, I argue that for the same reason, we must understand how this technology functioned not only in relation to musical performance per se, but also in what we consider today as non-musical settings, such as mathematical astronomy, the standardization of weights and measures, and divination techniques. Early Chinese authors thought about sound as resonating qi emanating from the cosmos. Its calculation, manipulation, categorization, and measuring were central to the synchronization between the human and cosmic realms. Part one of the dissertation discusses the gradual introduction of cosmological ideas into existing musical systems around the mid-third century B.C.E. As a result, some texts began discussing sound in numerical terms, as part of theories that aimed to measure the regularities of cosmic processes. Part two explores developments in acoustics and the concept of cosmological sound, through an analysis of a case study from the Western Han: Jing Fang 京房 and his tuning theory, which divided the octave into sixty tuning standards. I also provide an annotated translation of the first section of the “Treatises on Tuning Standards and Mathematical Astronomy” (“Lüli zhi” 律歷志) in the History of the Later Han. Part Three explores the concept of imperial control in Wang Mang’s brief Xin dynasty, examining the connections between sound, metrological practices, and the ideologies and philosophies that provided cosmological meaning to metrological choices. I argue that despite the court’s rhetoric of universal standardization, anchored in the dimensions of the Huangzhong pitch pipe, in reality these acts of standardization may not have succeeded far beyond the court’s immediate sphere of influence.