I recently acquired a large amount of Philip Glass' music. Right now, I am listening to "Einstein on the Beach", an Opera of his.
This is very trippy stuff, and features vocals and a symphony playing in very hypnotic time signatures.
Anyone who enjoys Ambient, Electronica, Prog Rock, Jazz, Post-Rock, Experimental, or music of any kind will enjoy this.
Here is a song from it:
Act III, Scene 1: Trial/Prison