I would think that many of you know of this opera by Philip Glass, Einstein on the Beach.
I haven't seen it, but I've listened to some pieces of it, and I find it very calming. I feel sorry for the singers though, must be painful to count to eight over 9000 times.

[youtube:1dxvzu2i]http://www.youtube.com/watch?v=WmX_GgozpQs[/youtube:1dxvzu2i]

Note, this music is from '76