Bela Bartok's Music for Strings, Percussion and Celesta, specifically Andante tranquillo and Adagio, though parts of Allegro molto might also qualify.
Samual Barbar's Adagio for Strings, Krzystof Penderecki's Threnody For The Victims Of Hiroshima For 52 Stringed Instruments and De Natura Sonoris II For Orchestra (which sound very much like the music from Altered States by John Corigliano), Space Requiem by Stomu Yamash'ta, and Title music for the movie The Bounty by Vangelis Papathanassiou are honorable mentions.
I have a feeling I'd have a lot of fun going through your music library. The Barber Adagio
and the Penderecki Threnody
would definitely make my list for this thread.
It's a good flesh-creepy one but I'm sure it can be topped. The use of Ligeti (apparently without his permission) in Space 2001 is fairly hair-raising in parts.
What happened with 2001
was that the "scratch track"--an assemblage of already-recorded pieces of music used to work out timings and feel for the scenes to be filmed--ended up being deemed preferable to what hired composer Alex North produced; the permissions may have been worked out after the fact - I'm not sure about that. If you listen to the music North composed for the film, it's clearly imitative and derivative of what was actually used, but fails to have equal impact. The Ligeti music is what I like most about the soundtrack, though I'll admit also to often hearing Strauss' "Blue Danube" waltz in my head while watching many spaceship and docking sequences, both fictional and actual.
For foreboding, one thing I can recall was from Dead Poets Society
- the music which plays as Robert Sean Leonard's character has decided he's going to off himself and pulls the gun out of his father's desk. I haven't seen the movie in years but I definitely remember getting a serious "uh-oh, something very bad is about to happen" sense from the music.