Young people in the criminal justice system experience significant health and wellbeing issues that often stem from poverty and disadvantage and, in turn, are linked with offending and reoffending behaviour. There is ongoing interest in interventions such as participatory music programmes that seek to foster social reintegration, support mental wellbeing and equip young offenders with life skills, competencies and emotional resilience. However, there is a need for a situated understanding of both positive and negative experiences that shape potential outcomes of music projects. This article reports on a research study undertaken between 2010 and 2013 with 118 young people aged 13–21 years across eight youth justice settings in England and Wales. Using mixed methods we explored the experiences of young people and their responses to a participatory music programme led by a national UK arts charity. Here, we explore the impact of young people's encounters with music and musicians with reference to the notion of ‘musical affordances’ (DeNora , ). We examine the ways that such affordances, including unintended outcomes, are mediated by features of the youth justice environment, including its rules and regulations, as well as issues of power, identity and social relations.