If you ever wondered what ambient music is all about, you could do worse than listen to the soundtrack by Brian Eno that accompanied the stunning visuals of NASA's Apollo missions to the moon. Created with an intoxicating mixture of acoustic and electronic, the music makes the now-classic space travel images more magical and memorable, introducing a dreamlike element to scenes of cold reality. "An Ending (Ascent)" is about as close to an actual tune as you'll get, but, as with every track, a shining example of what ambient music reveals about itself--slowly and carefully. --Paul Clark