I have been looking for some really good ambient music for my haunted house for awhile . I think I have found a few selections. The "Haunting Villisca" soundtrack by David James Nielsen has some great subtle but eerie tracks well worth a listen . Also David Shore's soundtrack for "The Beast" has great stuff. Not so much discernible melodies, but more of mood setting scores. Go find and listen.

If you layer atmospheric sounds over the top of these soundtracks, you can really amp up the mood of your haunt.