Raison D'être (French for "reason to be") is the name of a Swedish band, whose sole member has always been Peter Andersson. This is not to be confused with another identically-named individual making music in a similar vein, under the band name Deutsch Nepal.
The music produced by Raison D'être is variously darkwave, dark ambient, and soundscape in nature. For example, synthesizers might play a droning melody over the sound of metal scraping together. Andersson often mixes tapes of Gregorian chant with his own keyboard and percussion playing.
Taken from Wikipedia - http://en.wikipedia.org/wiki/Raison_d%27etre