Hi. For tagging my mp3 files I use Picard/MusicBrainz which is - im my opinion - the best tagger/DB combination.

But before writing the new tags (that the tagger fetches from the Internet) to the file, I would like to compare the new id3 data with the old one to see the differences. Picard is not sufficient.
I want to see the changes made to the file in both id3v1 and id3v2 RESPECTIVELY! And as far as id3v2 is concerned I'd like to see changes to all tag fields, even when the existing id3 tag has user defined fields.

Ideally I would look for a diff tool (like windiff), but for audio tags. The program should have a left and right pane where the old and the new metadata is displayed respectively and differences are highlighted. And it should be possible to switch between id3v1 and v2.
That would be perfect. Otherwise, it would also be helpful (though much more work) to be able to export both the id3v1 and v2 data respectively (all existing fields, including user-defined ones) to plain text files (for subsequent diff comparison in another application). Do you know a program with such an exporting function ?

Or do you have other ideas to solve that problem ?
I mean, I cannot be the only one who tags his music collection and wants to avoid losing important tag information...
Thanks a lot for your support!

sorry, bot nobody got any ideas ... ?
This is a quite common problem though, so how did you resolve that issue for yourself ?

this tends to be a problem of one app updating the ID3v2.3/4 tags but not the ID3v1 tag. They get out of sync. I recall fb2k reporting the id3v1 tag info in some cases. I solved this problem for myself in removing all my id3v1 tags (which I never actually needed it turns out) and using only ID3v2.3 tags. This way I don't have to deal with tag sync issues. You can remove v1 tags in fb2k, but I actually use mp3tag for my tagging needs and I'm quite pleased with it.

Sorry for the late reply, mail notification didn't work ...

thanks for your answer, but that's not what I meant.
I want to compare the new id3 data with the old id3 data. Not id3v1 vs. id3v2 ! Please see my OP for full details.