This article examines the history of the concept of the soul as harmony—as opposed to merely being like a harmony— in sixteenth-century England, demonstrating how debates over music’s morality in sixteenth-century England were a catalyst for theorising an increasing affinity between music and the soul. At the beginning of the sixteenth century, English writers valued music primarily for its restorative qualities or its potential to instil virtue, akin to arguments in Aristotle’s Politics. As attacks on music intensified mid-century, defenders turned to more Platonic views of music, gradually going as far as arguing that the soul itself was a harmony. As I demonstrate, however, music’s defenders trod a fine line in using this concept which had been challenged since classical times and caused problems for Christian theology and the notion of the immortal soul. Nevertheless, by the seventeenth century, the pervasiveness of the language of soul-harmony was such that it continued to be influential in the seventeenth century as a tool for conveying the emerging new medical and cognitive theories.