Sure... but -

1) It would have to be in some kind of ancient language, whether in-game, like Hylian, or real-world, like Sanskrit, Arabic, Latin, Hebrew, and etc. Japanese and English opera would feel like a bit of a cheat if you know what I mean.
2) Dark overtones. I don't mind sunshine-y, holy places having nice music, but since you're talking more specifically about boss fights here, each one would need its own *ORIGINAL*,
powerful piece.
3) No MIDI crap. Need I say more?... Zelda should be at the age where its ready to mature into orchestrated music, be it vocal or not.

Thank you for reading SL's list of complaints, and have a nice day!

Oh, and by the way, good to be back on ZU! (I haven't posted in at least a month).