Aleatoric music is music in which some element of the composition is left to chance, and/or some primary element of a composed work's realization is left to the determination of its performer(s). The term is most often associated with procedures in which the chance element involves a relatively limited number of possibilities.

Pierre Louis Joseph Boulez was a French composer, conductor and writer, and the founder of several musical institutions. He was one of the dominant figures of post-war contemporary classical music.