This article uses three well-known members of Rudolf II's imperial court—the astronomer Johannes Kepler, the composer Philippe de Monte, and the adventurer Kryštof Harant—to delineate some ways music helped Europeans understand identity and difference in the early modern period. For Kepler, the unfamiliar intervals of a Muslim prayer he heard during the visit of an Ottoman delegation offered empirical support for his larger arguments about the harmonious properties of Christian song and its resonances in a divinely ordered universe. For Harant, listening and singing were a means of sounding out commonalities and differences with the Christians and Muslims he encountered on his travels through the Holy Land. Monte sent his music across Europe to the English recusant William Byrd, initiating a compositional exchange that imagined beleaguered Bohemian and English Catholics as Israelites in exile, yearning for Jerusalem. Collectively, these three case studies suggest that musical thinking in Rudolfine Prague did not revolve around or descend from the court or sovereign; rather, Rudolf II's most erudite subjects listened, sang, and composed to understand themselves in relation to others.