The only place I know of right off the bat is the Mod Archive... But you probably want more orchestra-sounding music, so you'd have to look harder, and I'm not sure what kind of file types you can use in your game, so you'd probably have to convert the files. I don't know of any other places, save for VGMusic, but I don't think that's what you're looking for.

I guess what I'm trying to say is, I'm of no help at all! :P