Although music was integral to masques, the genre’s visual extravagance tends to overshadow its acoustic elements in scholarly and classroom discussions. This chapter focuses on “Sweet Echo,” the Lady’s song in Milton’s A Mask Presented at Ludlow Castle (Comus), which was performed in 1634 by 15-year-old Alice Egerton. The unusual level of detail that survives about this masque’s performance history, combined with the musical settings extant in Henry Lawes’s autograph manuscript, now held at the British Library, facilitates a suggestive evaluation of early modern song in terms of the rhetorical interplay between lyric, musical setting, and performance context. It also constitutes a striking case study for considering the acoustic impact of women’s singing voices. Milton’s depiction of temptation and self-discipline in Comus, whose moral message is encapsulated in miniature in the Lady’s performance of “Sweet Echo,” hinges on his audience’s experience of song as an acoustic, embodied, and gendered phenomenon.