When I first bumped in to DriveThruRPG I did not expect to see anything even close to mood music and sounds for RPG settings. When I did, I was at first aghast, thinking I'd stumbled on to some horrible form of Muzak. Thankfully, I did stumble into music here and it is certainly not Muzak.
City of the Dark Elves is a moody, deliberate piece with haunting background vocals (or simulated voices) and carries with it a great, dark quality. It puts me in mind of Mike Oldfield or other "new age" artists I gravitated to in my past.
It's probably not something you'll put in your commuting playlist on your iPod but it certainly works for gaming. It's background enough not to take over but pervasive enough to insert itself firmly in to your game.
My only hesitation with recommending this is the price. When you can get 5 minute songs just about anywhere online for $0.99 or $1.29, the current price of $2.99 seems just a bit high.