Messiaen allegedly quoted over 250 bird songs in his operatic work.

Messiaen’s great epiphany occurs in the fifth tableau, in which Francis meets a Musician Angel on the road. The episode is taken from Franciscan hagiography, according to which the friar once fainted after hearing an angel play a viol. He told his brethren, “If the Angel had played one more note—if, after down-bowing, it had made an up-bow—from unbearable sweetness my soul would have left my body.” In Messiaen’s version, the Angel prefaces his concert with lines borrowed from St. Thomas Aquinas: “God dazzles us by an excess of truth. Music carries us to God in default of truth.”

They also talk about how Messiaen envisioned the Resurrection as being at atomic explosion. His obituary, and a Wikipedia entry on St Francois d’Assise.