Iannis Xenakis (1922-2001) was a Romanian-born French composer, architect and mathematician who initiated the musique stochastique, a music composed with computers and based on mathematical probability systems.
Xenakis was born into a wealthy family of Greek descent and moved to Greece in 1932. He fought in the Greek Resistance in World War II, losing an eye. After graduating from the Athens technical institute in 1947, Xenakis was expelled from Greece for his political activities. He moved to Paris, where he was associated with the architect Le Corbusier for 12 years. At that time, he designed the Philips Pavilion for the International Exhibition in Brussels in 1958. At the age of 30, he seriously took up musical composition, taking lessons from Darius Milhaud and studying composition with Olivier Messiaen at the Paris Conservatory in 1950-1962. Following Messiaen's suggestion, he began to use mathematical models in composing his musical pieces.

His formalistic approach was rare among European composers who largely embraced serialism. In 1954, he began experimenting with stochastic music in the composition Métastasis. Xenakis' article "La Crise de la musique sérielle" (1955; "The crisis of serial music") explained his rigorously logical techniques in which performers - playing mostly standard instruments - are guided by a specially developed notation to produce sounds determined by a computer programmed by the composer.


Xenakis' experiences with the work Achorripsis (1958) for 21 instruments prompted him to formulate the rules of composition. These rules were extended in the program for ST/10-1,080262 (1956–62); the title symbols indicate that it is a stochastic piece, the first piece for 10 instruments, "computed" on February 8, 1962. Several other compositions, including ST/4-1,080262 for string quartet, Atrées (Hommage à Blaise Pascal) for 10 instruments and Morisma-Amorisma for 4 instruments, were based on the same program. In this series of works, he used an IBM 7090 computer to control note sequence, instrumentation, pitch, duration and dynamics. The performers are not free to improvise, but the resulting sound is fluid, homogeneous and natural.
Xenakis' long collaboration with the Ensemble Instrumental de Musique Contemporaine de Paris resulted in frequent performances and recordings of his works for chamber ensemble. In 1966 he founded the Center for Mathematical and Automated Musical Studies. Other works by Xenakis are: Polla ta dhina for children's choir and orchestra (1962), Akrata (1964–65) for 16 wind instruments and Cendrées (1974) for choir and orchestra. He also composed pieces exclusively for electronic reproduction, such as Polytope of Cluny (1972), sound and light space with 7-channel electronic tape, and Mycenae Alpha (1978), a stereo tape made on a UPIC computer, as well as works involving both people and electronic components, such as Pour les Paix (1982) for mixed choir, electronic tape and narrators. O-mega (1997) for percussion and ensemble was his last piece. His published books include Formalized Music: Thought and Mathematics in Composition (1971; published partially in French as Musicques formelles, 1963) and a transcription of his 1976 Master's thesis, Arts/Sciences: Alloys (1985; published originally in French, 1979).