In early modern North India, knowledge systems developed simultaneously in multiple “classical” and “vernacular” languages. This article examines the processes of multilingual knowledge transmission through an analysis of a Brajbhasha (classical Hindi) music treatise, the Sangitadarpana (“Mirror of Music”) of Harivallabha (ca. 1653). Harivallabha was translating a recent Sanskrit work of the same name: an old-fashioned treatise that nonetheless proved extremely influential in Persian and other Sanskrit works, as well as in miniature painting. This article examines the implications of the vernacular rendering of the Sangitadarpana and Harivallabha's seminal influence on the musicological intellectual culture that followed in his wake. Drawing on other translations and treatises in other forms of Hindi and Bengali, the article also considers the limits of Brajbhasha's circulation, and the wider implications of using a vernacular language for reading, listening, visual, and performance practices.