The opera Gawain (1991; revised 1994 and 1999) brought together Harrison Birtwistle and the poet David Harsent in a reworking of the late fourteenth-century narrative poem Sir Gawain and the Green Knight. That Birtwistle asked Harsent to make a large number of alterations to his original libretto has already been documented. The present article, which draws on the sketching processes of both librettist and composer, reveals the nature and the ramifications of those changes. The discussion is particularly concerned with the contradictions and multiple narrative layers that resulted from the Harsent–Birtwistle collaboration, and with the composer’s suggestion that there is both a secret drama in the orchestra, and instruments that function like unheard voices. A consideration of Birtwistle’s sketches also reveals a preoccupation with line, in particular with finding different ways of shadowing vocal and instrumental parts, and ambiguously shrouding originary lines in layers of varied reflection. These musical devices represent Birtwistle’s response to Harsent’s interest in divided subjectivity, and to the idea that Gawain should develop a sense of his own identity.