As a long-serving exemplar of late-'60s hippie values, this minimalist icon has aged with a chilled-out grace. He's allowed younger composers like Nico Muhly to remix his composition In C, and has—albeit gently—rocked out in the company of his guitarist son, Gyan Riley. Their collaborations on half-improvised boogie woogie opuses like “MissiGono” have a humorous and relaxed air.