Boulez was a world-famous conductor. He conducted many of the world's greatest orchestras. He was the chief conductor of the BBC Symphony Orchestra from 1971-1975, the New York Philharmonic from 1971-1977 and was Conductor Emeritus of the Chicago Symphony Orchestra. His concerts usually consisted of music by the great 20th century composers such as Alban Berg, Claude Debussy, Gustav Mahler, Arnold Schoenberg, Igor Stravinsky, Béla Bartók, Anton Webern and Edgard Varèse—as well as lots of new music which he conducted when it had just been written.