This paper estimates the long-term causal effects of music proficiency on emotional intelligence and mental health. Leveraging the staggered rollout of a school orchestra program as a quasi-experimental setting, we identify the causal impact of adolescent musical engagement. Our findings reveal that music training significantly improves both emotional intelligence and mental health into young adulthood. Specifically, musical proficiency fosters key non-cognitive traits, including self-motivation, optimism and adaptability, while also mitigating symptoms of poor mental health, including depression and anxiety. These positive effects are particularly pronounced for males and second-generation migrants. Our evidence demonstrates that learning music has a lasting positive impact on non-cognitive skills, suggesting that universal educational music programs can be a powerful, long-term tool for human capital development and inequality reduction.