“Being for the Benefit or Mr. Kite,” by the Beatles, sounds very spooky, even though the lyrics describe an event which is supposed to be happy. I’ve looped the end of the song (the instrumental part) to make a 20-minute long Hallowe’en background tape to good effect.
There is an new song out that was made to benifit UNICEF.
It’s called Do they know it’s Halloween? and it’s pretty good.
A band called Shape of Despair did an instrumental called Night’s Dew. Very, very creepy.
In the “sinister songs” thread I provided several (legal) links to mp3s of songs that I considered sinister. Some of them are spooky too. You could do worse than to spend a half hour downloading and listening to them to see if any fit your playlist.
If the song “Choralone (live)” by Skinny Puppy doesn’t scare you, there’s something wrong with you. The scary strings, the choirs, the banging on metal, the incomprehensible gutteral vocals. Yikes. The clip right here (disc 1, track 13) is very representative of the entire album.
Also, perhaps Coil’s “How to Destroy Angels” album?
If the song “Choralone (live)” by Skinny Puppy doesn’t scare you, there’s something wrong with you. The scary strings, the choirs, the banging on metal, the incomprehensible gutteral vocals. Yikes. The clip right here (disc 1, track 13) is very representative of the entire song.
Also, perhaps Coil’s “How to Destroy Angels” album?
For spooky choral/classical music try John Tavener I like 3thunder Entered Her" but you’ll find “Song For Athene” more easily.
Werewolves of London by Zevron?
Mannheim Steamroller has great versions of these on their Halloween CD.
I see Bach’s organ music has already been mentioned – in addition to being great compositions, some of it is downright spooky.
If you can get a hold of the soundtrack to Requiem For A Dream, most of the songs from Winter are quite eerie, particularly the Lux Aeterna. Will probably leave your guests more depressed than spooked, though.
Speaking of Lux Aeternas, check out the one composed by Ligeti, featured in the soundtrack for Stanley Kubrick’s 2001 : A Space Oddysey . Very creepy, very atmospheric.
I can’t ever talk about darkly-themed creepy-sounding music without mentioning one of my favorite artists of all time, though: Dead Can Dance . One album in particular comes to mind – Within the Realm of a Dying Sun , the last 4 tracks in particular. You can listen to samples at the link I just provided. Lisa Gerrard provides some of the most haunting vocals I’ve ever heard.
Another work suffused with an eerie ambience would be Mike Oldfield’s Tubular Bells (AKA Soundtrack for The Exorcist), and Tubular Bells II . He’s come out with a third Tubular Bells album, but I have not had the chance to listen to it yet, so I cannot give a recommendation on it.
“Intruder” by Van Halen’s <i>Diver Down</i> album is sort of creepy.
If you have any Nine Inch Nails in your collection I’m sure there are some suitable creepy songs there.
The soundtrack to Halloween is great and incidentally was written and performed by John Carpenter himself.
I highly recommend Midnight Syndicate–especially their first one, “Born of the Night” (though all of them are great and sound like they’re exactly what you’re looking for).
I first heard MS at a local “Haunted House” type attraction in San Jose, and I immediately went out and bought their first CD. I’ve since bought all the rest too, as they come out. They have a booth at Gen Con and Origins every year, and I’ve gotten to know a couple of the guys involved (at least to the extent that they recognize me and say hi). They do fantastic moody Halloween/scary/goth atmospheric music.
The party was last night. Thanks for all the suggestions-- the guests (and more importantly, my wife! 
) really enjoyed the music. I was able to use a lot of the Bach organ works and bought the soundtrack to Psycho, supplementing it with some Depeche Mode, Pink Floyd, Bauhaus, and VU (etc.). The Midnight Syndicate tracks they made available on their website went over well, too (thanks, winterhawk11!)…
Again, thanks to all!
The middle section of Pink Floyd’s “Echoes” — the atonal section — sounds spooky as hell if you speed it up 2x.
Here are a few I like to cue up around Halloween:
–“I Walk on Gilded Splinters” by Dr. John
–“Voodoo Chile (Slight Return)” by Jimi Hendrix
–“Season of the Witch” by Donovan
–“Superstition” by Stevie Wonder
–“Creature with the Atom Brain” by Roky Erickson
–“Voices Green and Purple” by The Bees
–“Colma” by Buckethead
–“Psycho Killer” by Talking Heads
The Suite from the “Hush” episode of Buffy the Vampire Slayer. You can get it on Itunes.
Also, Kraanerg by Iannis Xenakis.
Okay, that’s going to drive me crazy. It’s from a movie sound track but I can’t be sure which one. Does someone else know? I’m thinking maybe Disney’s version of 20,000 Leagues Under the Sea?