Though the study of metrics and poetic verse has long informed phonological theory, studies of musical adaptation remain on the fringe of linguistic theory. In this paper, I argue that musical adaptation provides a unique window in speakers’ knowledge of their phonological system, which can provide crucial evidence for phonological theory. I draw on two case studies from my fieldwork in West Africa: tonal textsetting of sung folk music in Tommo So (Dogon, Mali) and the balafon surrogate language in Seenku (Mande, Burkina Faso). I show how results of these studies provide evidence for different levels of phonological grammar, the phonetics-phonology interface, and incomplete application of grammatical tone. Further, the case of the balafon surrogate language shows how studying music can be a valuable tool in language documentation and phonological description. Finally, preliminary study of Seenku tonal textsetting suggests important differences in the level of phonological encoding in vocal music vs. instrumental surrogate speech.