I've just found MP3TAG, and so far, I've found it really impressive.
I've mostly been using it for batch-processing of a folder (of MP3 files), usually removing comment fields, or changing the 'genre' field.
An unexpected side-effect: I've noticed that the BPM (beats per minute) field in many MP3 files that I've processed has been multiplied by 10. An odd thing, to be sure. Confirmed by reading the file back in Tag&Rename or other programs. Also, I just tried to test to see if it could be reproduced, but it doesn't happen consistently. So something seems to be triggering it. Ideally, you'd think that the field would not be touched. But perhaps if the field is placed after others that I've removed, it is recalculated...?
Has anyone seen this?