You mean C implementations that do not use libvorbisfile and libflac, respectively?

Hmm, as long as those libs both have separate calls to just get file metadata (without saying "I want to decode and play this file") then those will work fine. I'll look into them first.

Since you already seem to be on your way to WMA metadata support, I'll probably hold off on reinventing that particular wheel, and start with flac and/or ogg.