Olivier Messiaen
Messiaen had been asked in 1971 to write an opera for the Paris Opéra. At first he did not want to start such a large work, but in 1975 he was persuaded to accept the commission and began work on his Saint-François d'Assise.  It took him several years to compose.  It was performed in 1983.  Messiaen said that he preferred to call it a “spectacle” instead of an “opera”.