This essay tracks the historical-musicological context of the lemma “organi” / “organo” as it appears in Purg. 9.144 and Par. 17.44. Drawing from medieval treatises and monks’ descriptions such as Raban Maur, Notkerus Balbulus, Baldric of Dol, Aelred of Rievaulx, and Wulstan, the author uses intertextual evidence to show that Purg. 9.144 (“quando a cantar con organi si stea”) evokes a great pipe organ as was found in some medieval churches. The essay also argues that Par. 17.43–44 (“come viene ad orecchia / dolce armonia da organo”) should be understood as a polyphonic organum that serves the two-fold purpose of lending authority to the Commedia’s longest prophecy and of musically representing the harmonious reconciliation of the highs and lows in human life.