Olivier Messiaen (1908-1992) was an influential French composer, as well as organist at the church "La Trinité" from 1931 until his death. Musically very eclectic, he was influenced heavily by Hindu and Ancient Greek rhythms, as well as by the songs of birds, and transcribed hundreds of birdsongs himself worldwide. The titles and content of many of his works also contain references to Catholic doctrine, especially mysticism.
Messiaen was sent to a concentration camp during WWII. While incarcerated, he wrote his most freqently-played and recorded work, the Quatuor pour le fin du temps (Quartet for the End of Time), which was performed in 1941 by the composer and fellow inmates for an audience of prisoners and guards. Written for an instrumentation of piano, violin, cello, and clarinet, it is based on the following passage from Revelation 10 (KJV):
1And I saw another mighty angel come down from heaven, clothed with a cloud: and a rainbow was upon his head, and his face was as it were the sun, and his feet as pillars of fire ... 2and he set his right foot upon the sea, and his left foot on the earth .... 5And the angel which I saw stand upon the sea and upon the earth lifted up his hand to heaven, 6and sware by him that liveth for ever and ever ... that there should be time no longer: 7But in the days of the voice of the seventh angel, when he shall begin to sound, the mystery of God should be finished ....
A crucial part of Messiaen's unique musical language, which he outlined in a lengthy introduction to the aforementioned Quartet for the End of Time, are the so-called "modes of limited transposition," in other words, symmetrical scales that are made up of smaller patterns. Examples of this are the whole-tone and octatonic scales.
Messiaen's music for organ assumes a prominent place in the repertoire, and the composer himself recorded all of his works in the 1960s on the organ at "La Trinité."