The answer seems to be "kind of."
Here's a version of the FF7 boss theme injected into an ancient cave ROM.
It isn't perfect, but it's a proof of concept, and could probably be used to bring in all sorts of music if I wanted to. As it stands, I don't know if/where I'll even use this or other tracks, though I think it would be neat in particular to bring in some SD3 or Legend of Mana tracks.
Here's an SPC Capture.