In the first part of the 20th century, classical music was stripped of its majesty and injected with a healthy dose of discord and dissonance by avant-garde pioneers like Arnold Schoenberg, Pierre Boulez, and John Cage. Then in 1950s California and New York, a new form of contemporary classical music emerged: minimalism. "Tones, Drones and Arpeggios" is a terrific two episode BBC Four documentary on American minimalism pioneers La Monte Young, Terry Riley (above), Steve Reich, and Philip Glass who reimagined "classical" music and had a massive and continuing influence on punk, experimental, ambient, and electronic music.
Watch Episode 1 below. More about the documentary here: "Tones, Drones and Arpeggios: The Magic of Minimalism"