Geoffrey Chaucer’s (1343–1400) repeated phrases are a conundrum. Nancy Mason Bradbury has referred to them as ‘formulas’; Derek Brewer has described Chaucer’s poems as having a ‘traditional formulaic style’. But why would a literate poet make use of a device that tends to be associated with orality? This paper offers an alternative comparandum for Chaucer’s repeated phrases: the refrain. As well as writing narrative poetry, Chaucer acknowledges at the end of The Canterbury tales that during his career he has written ‘many a song and many a leccherous lay’ (‘many a song and many a lascivious ditty’). Few of these songs survive, but one in particular—a ballade known as ‘To Rosemounde’—shows Chaucer to have a keen facility with the paradoxical potential of the refrain. ‘To Rosemounde’ survives in only one manuscript copy, paired with Chaucer’s narrative poem Troilus and Criseyde. This manuscript pairing, and Chaucer’s frequent presentation of Troilus and Criseyde itself as a ‘song’, invites a comparison of the poem’s repeated phrases to the refrains of a song lyric. In Troilus, phrases that are repeated at crucial moments—such as ‘I can no more’ and ‘without more’—emulate refrains by holding repetition and closure in an unstable synthesis.