Ambient or non ambient?
It depends on how intrusive you want it to be. The music I use when GMing is most often semi-ambient. Enough to contribute the appropriate mood without distracting the players too much.
For instance, when running Ravenloft, I don't make use of horror soundtracks, (or anything even
remotely Goth inspired) Instead, I use tracks such as Jean Michelle Jarre's
Waiting for Cousteau. The track itself is about forty minutes long, and if you put in on repeat it will last you most of the night. The players will almost forget it is there, but nevertheless feel the highly claustrophobic and tense atmosphere it brings to the game.
The Man Who Fell To Earth - David Bowie
Bowie had nothing to do with the Soundtrack to this film. If you want to listen to the kind of music that he
would have written for it, chuck on second side of LOW. Ziggy Stardust isn't really appropriate either (IMHO) Don't get me wrong, its a great album, (OK, a really great album) but for a outer space game? Maybe you could get away with Five Years and Starman.
Good Bowie Choices...
Hmmm...
If you are looking for the sound of Urban Decay, you can't go past Three tracks from Diamond Dogs - Sweet thing - Candidate - Sweet thing reprise. For some Chaos and Suppressed Rage you might go with some material from 'Scary Monsters and Super Creeps.' or "1.Outside"
However, it seems to me you are looking more for the song sort of stuff...In that case have a listen to Ashes to Ashes which, apart from providing a bookend to Space Oddity, also has a fantastic Soundscape.
Other Artists...
"Flash" (Queen) - Big, Anthemic, and Space Opera-y type.
"Oxygene (1-6)" (JMJ) - If you want a "Hitchhiker's guide to the galaxy" feel.
Selected tracks From "Apollo: Atmospheres and Soundtracks" By BrianEno, Roger Eno, and Daniel Lanois.
I'll go have a look at my album collection.
Shallow, but only on the surface