Research provides compelling evidence linking music-making to academic achievement and increased well-being for disengaged students. However, in the Australian context, education policy has narrowed its focus to literacy and numeracy, with an associated 'accountability' framework of mandated assessment and reporting practices. Within this context teachers are being asked to demonstrate how, through their pedagogical practices, they meet the needs of all their students. As a result of this, differentiation has become the lens through which student learning and engagement is being monitored. Drawing on data from a large state secondary school, this paper examines how a differentiated music curriculum is being implemented to support student agency. We demonstrate that, through a range of formal and informal music programs, agency is enhanced through the development of self-reflexive and self-referential learning practices. However, we suggest that differentiation, alone, does not unmask the reasons behind students' different learning experiences nor does it necessarily redress entrenched educational inequalities. We also suggest that the 'moments' for student agency, created by these music programs, may have as much to do with the 'fragile' position of music within the broader school curriculum where the spotlight of high-stakes testing is directed elsewhere.