Pierre Boulez radically expanded classical music’s possibilities. Born in 1925 in Montbrison, France, Boulez enrolled at the Paris Conservatory in 1942 and discovered serialism, a compositional method that appealed to both his mathematical sensibilities and rebelliousness. His 1954 chamber work, Le marteau sans maître, which he revised in 1957, established Boulez’s careful sense of structure as well as his habit of reworking his pieces. Later works would grant performers an unprecedented degree of agency, opening up new worlds of indeterminacy. Boulez was also chief conductor of the BBC Symphony Orchestra, music director of the New York Philharmonic, and a guest conductor of many orchestras around the world. In this capacity, he delivered canonical performances of contemporary pieces by Ligeti and Messiaen, and in 1996, he won a Grammy for the Cleveland Orchestra’s recording of Debussy: Nocturnes, Première rhapsodie, Jeux & La mer. Boulez’s belief in the power of the new took him far beyond the orchestra pit: From 1970 until the mid-’90s, he was director of IRCAM, the pioneering Parisian center for electronic music. He continued working well into his eighties before passing away in 2016.