Does anyone know what the "rid" tag is for?
This is probably a new tag in v3.00-alpha3.

It looks like an md5sum, but it is not. It could
be an md5sum of part of the tune, though.

Pim

Did you check to see if it might be an md5 of the track without any metadata (that is, minus any ID3 tags)? I'd check with and without the VBR header, too.

It's an MD5 of a portion of the tune -- the first 64Kb past the ID3v2, the last 64Kb before the ID3v1, and the middle 64Kb. It is used to identify a particular track with a good degree of uniqueness, so that we can do proper duplicate checking.

IIRC, emplode doesn't do this yet (Rio Music Manager does), and JEmplode supports the same scheme, for future compatibility.