I'm a composer if you need music (video is my second vocation). Just email me from my profile address. I can work with your budget. If not, maybe someone else has a library suggestion.
Go to a church with a real pipe organ. Ask if you can have someone play some slow plodding dimished stuff on it. Record it.
If you have never seen the orginal "Carnival of Souls" this would be a great time to go see it. If you can make sure you are seeing the restored / remasterd version from Englewood Entertainment.
I use firstcom music - they may have some cuts you may like.
If you want I could send you some links for you to preview.(save you some time- alot of music there.)
just shot me an e-mail if you like.