Olivier Messiaen (10 December 1908 – 27 April 1992) was a French composer, organist, and ornithologist. He entered the Paris Conservatoire at the age of 11, and numbered Paul Dukas, Maurice Emmanuel, Charles-Marie Widor and Marcel Dupré among his teachers. He was appointed organist at the church of La Trinité in Paris in 1931, a post he held until his death. On the fall of France in 1940 Messiaen was made a prisoner of war, and while incarcerated he composed his Quatuor pour la fin du temps ("Quartet for the end of time") for the four available instruments, piano, violin, cello, and clarinet. The piece was first performed by Messiaen and fellow prisoners to an audience of inmates and prison guards. Messiaen was appointed professor of harmony soon after his release in 1941, and professor of composition in 1966 at the Paris Conservatoire, positions he held until his retirement in 1978. His many distinguished pupils included Pierre Boulez, Yvonne Loriod (who later became Messiaen's second wife), Karlheinz Stockhausen, Iannis Xenakis and George Benjamin.
Messiaen's music is rhythmically complex (he was interested in rhythms from ancient Greek and from Hindu sources), and is harmonically and melodically based on modes of limited transposition, which were Messiaen's own innovation. Many of his compositions depict what he termed "the marvellous aspects of the faith", drawing on his unshakeable Roman Catholicism. He travelled widely, and he wrote works inspired by such diverse influences as Japanese music, the landscape of Bryce Canyon in Utah, and the life of St. Francis of Assisi. Messiaen experienced a mild form of synaesthesia manifested as a perception of colours when he heard certain harmonies, particularly harmonies built from his modes, and he used combinations of these colours in his compositions. For a short period Messiaen experimented with the parametrization associated with "total serialism", in which field he is often cited as an innovator. His style absorbed many exotic musical influences such as Indonesian gamelan (tuned percussion often features prominently in his orchestral works), and he also championed the ondes Martenot.
Messiaen found birdsong fascinating; he believed birds to be the greatest musicians and considered himself as much an ornithologist as a composer. He notated birdsongs worldwide, and he incorporated birdsong transcriptions into a majority of his music. His innovative use of colour, his personal conception of the relationship between time and music, his use of birdsong, and his intent to express profound religious ideas, all combine to make it almost impossible to mistake a composition by Messiaen for the work of any other western composer.