What kind of background music is used in a scene to make it horror/ spooky?

ok, usually outdoor sounds. Sometimes the sound of an owl, or have the character crunch through the snow or leaves, heightened the sound, so that that is all that is heard. Also, sounds of wolves or crickets in the background. Think of being in the middle of the forest at night, imagine what sounds you would hear, and then use those! Also, the one instrument thing works as well. Figure the score to the DARK KNIGHT. The Joker's theme music was a chello/violin mix to enhance his insanity, and it worked PERFECTLY!. Hope this helps!