Olivier Messiaen was a French composer, organist, teacher, and ornithologist whose music is distinguished by his deep devotion to Catholicism, exoticism, and nature. At the age of 11 he entered the Paris Conservatoire, studying organ and improvisation with Marcel Dupré and composition with Paul Dukas. In 1930, he became the principal organist at La Trinité Cathedral in Paris, a post he held for more than 40 years. His distinguished teaching career is marked by appointments in Darmstadt (1950-1953), his famous courses in harmony and analysis at the Paris Conservatoire beginning in 1947, and his appointment as professor of composition there in 1966. His impressive list of students includes Boulez, Stockhausen, and his second wife, keyboardist Yvonne Loriod, among many others. In synthesizing an individual style, Messiaen discovered in the music of Debussy the properties of "exotic" modes such as the whole-tone and diminished scales, calling them "modes of limited transposition." The inherent symetricalities of these modes enabled Messiaen to create progressions and melodies free of the tonic-dominant polarity of traditional tonal music, while remaining independent of the twelve-tone system as well. Messiaen was gifted with a strong sense of "synaesthesia" or hearing in colors. He often described his music in terms of "color progressions," also equating key signatures and collections (sets) of pitches with specific colors. At an early age, Messiaen developed a strong interest in rhythm, particularly fostered by Stravinsky's The Rite of Spring. His rhythmic investigations ranged from Gregorian chant, to ancient Greek poetic meters, to Indian raga, to gamelan music. He soon left regular metric divisions behind, although repetition remained an integral part of his rhythmic vocabulary. All of these elements are explained in great detail in his 1944 publication, Technique de mon langage musical (Technique of my musical language). In 1940, while a prisoner of war of the Germans, Messiaen composed Quatuor pour la fin du temps (Quartet for the End of Time). The quartet's unique instrumentation of piano, clarinet, violin, and cello was written for, and premiered by Messiaen and three fellow inmates while in detention; it became one of the great chamber works of the twentieth century. Messiaen was one of the first composers to apply serial techniques to parameters other than pitch (such as duration, register, and dynamics) in Mode de valeurs et d'intensités (1949) for solo piano. His interest in plain chant and rhythm led him to the ancient Greeks and Hindus, where he discovered processes such as nonretrogradable, additive, and subtractive rhythms. The Turangalila-symphonie of 1948 is the most synthetic of his early works. It features rich orchestration, imaginative use of tonal colors, Hindu rhythms, and a formal scheme that unfolds in large, block-like structures. Also of note here is one of the earliest uses of the Ondes Martenot, an electronic instrument capable of producing eerie glissandi, as well as monophonic melodies. Messiaen had a deep love of birdsong, and spent much time in the wild making extensive transcriptions, many of which would surface in his works, most notably in an arresting orchestral passage in Chronochromie (1960) and the monumental Catalogue d'oiseaux (Catalog of the Birds) (1958) for solo piano. His large body of organ music, composed primarily during his tenure as organist at the Sainte Trinite Cathedral, is highly idiomatic, colorful in harmony and registration, and rhythmically ingenious. From 1950, his Messe de la Pentecote (Mass of the Pentecost) is a collection of improvisations that he shaped into a composition. His only opera, St. Francis d'Assise, was completed in 1983.