Bases a music participation theory on findings in music education, ethnomusicology, and sociology of leisure. Posits six types of music participants: professionals, apprentices, amateurs, hobbyists, recreationists, and dabblers. Distinguishes each type by theoretical variations in cost-benefit relationships as perceived by participants. Discusses four research metahypotheses: typification, affective potency, social importance, and predictability. (DK)