Miserere

http://en.wikipedia.org/wiki/Miserere_(Allegri)

Miserere by Gregorio Allegri (also called "Miserere mei, Deus" - English "Have mercy on me, O God") is a setting of Psalm 51 (50) composed during the reign of Pope Urban VIII, probably during the 1630s, for use in the Sistine Chapel during matins on Wednesday and Friday of Holy Week. It was the last of twelve falsobordone Miserere settings composed and chanted at the service since 1514 and the most popular: at some point, it became forbidden to transcribe the music and it was only allowed to be performed at those particular services, adding to the mystery surrounding it. Writing it down or performing it elsewhere was punishable by excommunication. The setting that escaped from the Vatican is actually a conflation of verses set by Gregorio Allegri around 1638 and Tommaso Bai (1650 - 1718, also spelled "Baj") in 1714.

Eeerie sorta music.