No 20th-century composer has penetrated pop's consciousness like Philip Glass. Repetitive, hypnotic, and unapologetically beautiful, Glass’ style all but defines the popular concept of minimalism—a fraught term considering how rigorous the music actually is. (Glass once compared his work ethic to that of an athlete in training.) Songs like “The Grid,” from his soundtrack to 1982’s experimental documentary u003ciu003eKoyaanisqatsiu003c/iu003e, sound at once primitive and futuristic, orderly and ecstatic, like an Indian raga generated by a giant, unblinking machine. A fixture of the New York art scene in the ’60s and ’70s who continued to work as a taxi driver and plumber into his forties, the Baltimore-born Glass also helped redraw the boundaries of what a so-called classical composer could be. He set the template for modern opera with his epic 1976 work u003ciu003eEinstein on the Beachu003c/iu003e, and has scored experimental theater and Hollywood film, working with artists as varied as David Byrne, Allen Ginsberg, Martin Scorsese, and Ravi Shankar (with whom Glass studied in his twenties). Listen for his imprint in ’70s art-rock like David Bowie and Brian Eno's avant-leaning Berlin Trilogy, Donna Summer’s pulsing “I Feel Love,” house and techno music, and the lope of left-field hip-hop. It’s the sound of revelation through repetition and freedom through order.