This isn't music as much as it is sound effects.
Three years ago I created a piece of software that would play random sound effects endlessly until you stop the program. I used it for my own haunt and for the past three Halloweens it has worked perfectly. In fact, it's the one thing about my haunts that I didn't have any complaints about.
It is set up for my own particular haunt, but it can be customized (there is a readme file that should walk you through it). My haunt uses two speakers; a large one on the right (where all of the thunder gets panned to) and a smaller one to the left by the door. If that doesn't work for you, you can easily tweak with each and every one of the sounds. Also, there is a convenient little "Reverse Stereo" checkbox which will simply flip the pan settings, so sounds that would normally go to the right would go to the left, and so on.
The download is about 50 MB. That's about 1 MB for the program, and 49 MB of mp3s.
It is available at the following address:
http://www.trentdavis.net/files/SoundMachineSetup.exe
I am currently working on a new version that will incorporate surround sound, allowing you to pan the settings across 5 different speakers.
Let me know what you guys think. There was another post asking what people listen to when they are building props. Well, this is it for me. I just fire up my Halloween Sound Machine and listen away.