Well, you can't go wrong with Ominous Latin Chanting, of course, but here's some more tracks/albums that fit the Halloween theme.
Climbing Up The Walls; Fitter, Happier - Radiohead
Scoundrel Days - A-Ha - Scoundrel Days
A Day Without Me; Exit - U2
The Downward Spiral - Nine Inch Nails - The Downward Spiral
The Culling Of The Fold - The Decemberists - The Crane Wife (bonus track)
The Hazards of Love 3 (Revenge!); The Rake's Song - The Decemberists - The Hazards Of Love (A lot of The Decemberists' stuff is secretly creepy: Odalisque, We Both Go Down Together, Leslie Anne Levine; The Mariner's Revenge; The Chimbley Sweep; etc, etc.)
Gloomy Sunday - Billie Holliday (AKA, The Hungarian Suicide Song)
The Great Gig In The Sky - Pink Floyd - Dark Side Of The Moon
Miseria Cantare - AFI - Sing The Sorrow
Revolution #9 - The Beatles. (I created a backwards and slightly slowed down version just for myself. It's even creepier)
I'm Afraid Of Americans; All The Madmen; Running Gun Blues - David Bowie
Murder Ballads - Nick Cave & The Bad Seeds
Deep In The Woods - The Birthday Party
De Mysteriis Dom Sathanas - Mayhem (A Norwegian black metal band whose lead singer killed himself, then the bass player murdered the guitarist. This album was recorded while all that was going on.)
Television Rules The Nation - Daft Punk
The Land Of Rape And Honey - Ministry
Metropolis Part 2: Scenes From A Memory - Dream Theatre
Fire On High - Electric Light Orchestra (No, really)
#1 Crush - Garbage
Under Ice; Waking The Witch - Kate Bush
Hammerhead - The Offspring
Jenny Was A Friend Of Mine; Bones; Midnight Show; Leave The bourbon on The shelf - The Killers
Broken Witch - Liars
The Kids - Lou Reed
The Holy Bible - Manic Street Preachers
Gacy's Place: The Undiscovered Corpses - The Mentally Ill
Absolution - Muse
Reverie/Harlequin Forest; deliverance - Opeth
The Lonesome Waltz of Leonard Cohen; Richmond Is A Hole -Pageninetynine
Down By The Water; Catherine; We Float - PJ Harvey (to name a few)
Haunted - POE
Frankie Teardrop - Suicide
Soundtracks For The Blind - Swans
For Whom The Bell Tolls - Steven Baker & Carmen Daye
Here's my horror playlist with some additional notes:
- Romance - My Chemical Romance - I Brought You My Bullets, You Brought Me Your Love
- The Guitar Lesson - Steven Wilson - Cover Version IV (See also: Insurgentes)
- A Little Push - Hans Zimmer & James Newton Howard - The Dark Knight (Soundtrack) [The least-Batman-sounding track on the Batman album; See also: Batman Begins soundtrack]
- Raining Blood - Tori Amos - Strange Little Girls [This whole album has creepy and weird covers, notably her cover of Eminem's "'97 Bonnie & Clyde", not to mention her own songs, "Me And A Gun" and "Juarez"]
- Corpse (These Chains Are Way Too Long) - Passengers - Original Soundtracks 1
- Danse Macabre - Celtic Frost - Morbid Tales [Whole album's creepy & weird, but what do you expect from Swiss death metal?]
- Black Box Theme - Tom Waits - The Black Rider (Not his creepiest, but the best one that fit here. See also: pretty much every one of his albums has something dark on it)
- Slide - The Dresden Dolls - The Dresden Dolls (See Also: "Lonesome Organist Rapes Page-Turner")
- The Pass Where The Devil Can See - Roddy Bottum - Live Freaky! Die Freaky! (Soundtrack) [A claymation musical parodying the Manson family. The rest of the album is completely fucked-up, too]
- Helter Skelter - Siouxsie & The Banshees - The Scream (See Also: Rapture, Spellbound, Not Forgotten)
- Worlock - Skinny Puppy - Rabies
- Empty Sounds of Hate - Marilyn Manson - Antichrist Superstar (See also: Portrait Of An American Family)
- Pull/Pulk Revolving Doors - Radiohead - Amnesiac
- Subway Song - The Cure - Boys Don't Cry
- Lullaby - A Perfect Circle - Thirteenth Step (See also: Emotive, namely Annihilation, Imagine, Gimme Gimme Gimme and Counting Bodies Like Sheep To The Rhythm Of The War Drums)
- Isolation Cubicle 312 - Axis Of Perdition - Deleted Scenes From The Transition Hospital (Whole album, completely messed up and nightmare inducing)
- Crucifixus - Sarah Brightman & Company - Repo! The Genetic Opera (Soundtrack)[A mezzo-soprano singing in German about how she was blind, but now sees and everything is going to scream out]
- Please (single version) - U2 - Pop
- Viginti Tres - Tool - 10,000 Days (See also: Lateralus, especially "Faaip De Oaid"; "Disgustipated")
- Black Sabbath - Type O Negative - nativity In Black: A Tribute to Black Sabbath (Diabolus En Musica)
- black - Inhale - Breathe Hard, Breathe Deep (This guy is incapable of making music that doesn't make you want to piss yourself.)
- Doctor Finklestein/In The Forest - Amiina - Nightmare Revisited
- Bathory Erzsebet - Sunn O))) - Black One (Nothing like locking a claustrophobic guy in a coffin and letting him scream)
- Bonnie The Cat - Porcupine Tree - The Incident (See Also: In Absentia)
- Als Jakob Erwachte - Krzysztof Penderecki - Inland Empire (Soundtrack) [Everything Penderecki has composed gives heebies and jeebies. David Lynch got a little obsessed with this track while filming the movie and went a little nuts. See also: Threnody For The Victims of Hiroshima]
- The Unforgettable Fire - Hiro Goto & Adrienne Woods - Still Strung Out on U2
- Take A Bow - Muse - Black Holes And Revelations
Have fun storming the castle!