Messiaen entered the Paris Conservatoire at the age of 11 and was taught by Paul Dukas, Maurice Emmanuel, Charles-Marie Widor and Marcel Dupré, among others. He was appointed organist at the Église de la Sainte-Trinité, Paris, in 1931, a post held until his death. He taught at the Schola Cantorum de Paris during the 1930s. On the fall of France in 1940, Messiaen was made a prisoner of war, during which time he composed his ("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 for an audience of inmates and prison guards. He 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 Iannis Xenakis, George Benjamin, Alexander Goehr, Pierre Boulez, Karlheinz Stockhausen, Myung-whun Chung and Yvonne Loriod, who became his second wife.