Iannis Xenakis (1922-2001) was a composer, architect and mathematician. He was born in Romania into a Greek family and moved to Greece aged ten. During World War II, he fought in the Greek resistance movement. After graduating from the Athens institute of technology in 1947, he had to leave Greece due to his political activities and moved to Paris. There, he worked as an architect with Le Corbusier. Starting in 1950, he concentrated on his musical education and studied composition under Olivier Messiaen. Using mathematical models in his compositions, he established the system of stochastic music. Among his most important works are Metastaseis (1953–54) for orchestra, which introduced independent parts for every musician of the orchestra; percussion works such as Psappha (1975) and Pléïades (1979); compositions that introduced spatialization by dispersing musicians among the audience, such as Terretektorh (1966); electronic works created using Xenakis's own UPIC system for computerised musical composition; and the massive multimedia performances Xenakis called polytopes. In 1966, Iannis Xenakis established the Equipe de Mathématique et Automatique Musicales in Paris. Between 1967 and 1972 he taught at Indiana University and later as a visiting professor at the Sorbonne. His teachings were published in various books and articles, most importantly Formalized Music: Thought and Mathematics in Composition (1971). In 1999, two years after finishing his last work O-mega for percussion soloist and chamber orchestra, Xenakis received the Polar Music Prize.