Previous studies on the effects of leisure activities on skill development do not discuss whether such activities are complements or substitutes. Comparing to which extent various extracurricular activities influence skill development brings us closer to understanding the formation of educational inequalities as well as the mechanisms behind skill production. Using data from the German Socio-Economic Panel, our study compares the role of music and sports for the development of cognitive and non-cognitive skills during adolescence. We use parental taste as an instrumental variable to account for the non-random choice between these activities. Our preliminary findings suggest that music is better than sports for increasing adolescents' ambition and optimism about future success.