Mogwai - Auto Rock
I've been looking for somewhat relaxed, mellow and repetitive music to listen to as ambiance. Most ambient music, however, has no dynamic contrast and gets a little boring. Both of the above songs have great climaxes, Auto Rock being essentially one big crescendo. They're a forerunner of post-rock, rock instrumentation (plus some piano) used in rather relaxed and melodic ways.
@.Sup: Yes, big fan of Jazz here, I play all flavors of sax. I've been listening to something a friend tells me is "acid jazz"; electronica with some jazz instrumentation. Amon Tobin does mostly electronica, but the Permutation album has a lot of jazz on it, Nova being my favorite. If you're not familiar with Amon Tobin, but watch Top Gear, you may recognize Easy Muffin.