. I don't know much about Ogg, don't they have their own non-ID3 tag format or something?

Yes, the Ogg "comment" format is (for both better and worse) more open-ended with no strict definitions as in ID3. In practice, though, with softwares like EasyTag, what I see is Ogg comment/tag support implemented in a way that mimics MP3/ID3. I do not know if there are any tools out there to build/read/write a custom Ogg comment format, but if there are, I don't think they have made it into any Tag editors. The notion appeals to me, though...dream up your own tags....multiple subgenres, mood fields, whatever. I was also thinking of things like all credited musicians on a track with instruments, recording studio, songwriter, etc. Perhaps these are getting into ID3 and I haven't been paying attention.

Anyhow, open-ended possibilities, but short on implementation for now. That GetID3() lib says it will write to Ogg, so when I get home in a few weeks and get some time I may have to add lyrics to an MP3, write its tags to Ogg and see what happens...see if that is a starting point.