One of the more common ways for people to add hidden tracks on a CD is for the last track to contain two songs separated by silence. Since in MB we follow the TOC of the CD, we have to store these as a single track in the database, e.g. https://musicbrainz.org/recording/5aba1945-bc53-46e5-886c-b9688de5e331 but people often split the files and want to tag them separately.

We've been able to link to the original songs for a while now using https://musicbrainz.org/relationship/1b6311e8-5f81-43b7-8c55-4bbae71ec00c and we've finally made it possible to put the relationships in order. That information is returned in the webservice, see the ordering-key element on https://musicbrainz.org/ws/2/recording/5aba1945-bc53-46e5-886c-b9688de5e331?inc=recording-rels

It would be nice if Picard could add support for these now, so that people can tag these as separate tracks if they want to. I imagine being able to right click a track which has these relationships and have an option "Split tracks" which would replace the current recording with the individual ones (shifting the track numbers down, as appropriate), so the above example would go from

• 16: Freedom of Speech Won't Feed My Children / We Are All Bourgeois Now

to

• 16: Freedom of Speech Won't Feed My Children
• 17: We Are All Bourgeois Now

I'm not sure how I would handle loading previously tagged files. It should at least match both tracks to the combined track. Ideally it would detect that they were split and automatically split it again.

A long time ago bitmap made a plugin which attempted to implement this. I'm not sure if he still has that lying around and I imagine it won't work now, but if he (or someone else) has a copy, it might be useful to see how he originally did it.

Older forum threads about it:
http://forums.musicbrainz.org/viewtopic.php?id=4123
http://forums.musicbrainz.org/viewtopic.php?id=2868