Giannis Klearchou Xenakis was a Romanian-born Greek-French avant-garde composer, music theorist, architect, performance director and engineer.
After 1947, he fled Greece, becoming a naturalised citizen of France eighteen years later. Xenakis pioneered the use of mathematical models in music such as applications of set theory, stochastic processes and game theory and was also an important influence on the development of electronic and computer music. He integrated music with architecture, designing music for pre-existing spaces, and designing spaces to be integrated with specific music compositions and performances.
Among his most important works are Metastaseis for orchestra, which introduced independent parts for every musician of the orchestra; percussion works such as Psappha and Pléïades; compositions that introduced spatialization by dispersing musicians among the audience, such as Terretektorh; electronic works created using Xenakis's UPIC system; and the massive multimedia performances Xenakis called polytopes, that were a summa of his interests and skills.