Incorrect artist tags when collabs exist

[abdulocracy]

I've come across a bug where artist tags for albums are incorrectly assigned, even after a full rescan.

One example I can give is the artist Burial and the collab Burial + Blackdown, in my library. I have many albums by Burial, and only one album that is a collab. LMS categorizes every single Burial album as Burial + Blackdown, which is incorrect. Here are screenshots illustrating the issue:

Only the collab album is show under Burial:

Under Burial + Blackdown, all Burial only albums are shown, plus the one collab album:

Here's the release page of one of the incorrectly labeled albums:

[epoupon]

Hmm I have an idea. could you paste the output of the lms-metadata command on one track of the collab album and on one track of the non collab album?

[abdulocracy]

burial.txt
burial-blackdown.txt

[abdulocracy]

It seems to parse the artist metadata correctly.

[epoupon]

Actually there is something weird in the metadata:

[ALBUM ARTIST] = Burial + Blackdown
[ALBUMARTIST] = Burial + Blackdown
[MUSICBRAINZ_ALBUMARTISTID] = 9ddce51c-2b75-4b3e-ac8c-1db09e7c89c6

As opposed to:

[ALBUM ARTIST] = Burial
[ALBUMARTIST] = Burial
[MUSICBRAINZ_ALBUMARTISTID] = 9ddce51c-2b75-4b3e-ac8c-1db09e7c89c6

Notice the same MBID for AlbumArtistID here. LMS has a single MBID entry per artist (MBID is meant to be unique), so in your case I guess it just gets erased with the last one scanned.
Not sure how to handle this, the tags look questionable?

[epoupon]

I tested these two files with picard and here is what I get:

[ALBUMARTIST] = Burial + BlackDown
[MUSICBRAINZ_ALBUMARTISTID] = 9ddce51c-2b75-4b3e-ac8c-1db09e7c89c6*SEP*c583b756-a74d-4010-af7e-61482ab8aeaa
Album artist: Burial + Blackdown 'Burial + Blackdown'

Well, as the number of entries in MUSICBRAINZ_ALBUMARTISTID and in ALBUMARTIST don't match, LMS just ignores the MBID in that case and only consider ALBUMARTIST. That is not good since you won't be able to link Burial + Blackdown with Burial or Blackdown

Editing the metada by hand and setting the multiple values solves this though:

Gives:

[ALBUMARTIST] = Burial*SEP*BlackDown
[MUSICBRAINZ_ALBUMARTISTID] = 9ddce51c-2b75-4b3e-ac8c-1db09e7c89c6*SEP*c583b756-a74d-4010-af7e-61482ab8aeaa
Album artist: Burial (9ddce51c-2b75-4b3e-ac8c-1db09e7c89c6)
Album artist: BlackDown (c583b756-a74d-4010-af7e-61482ab8aeaa)

Not sure why picard uses a single value here, as in the MB database it really seems to be two different artists?

[abdulocracy]

It seems you're right, the identical IDs are not ideal. I'm using Beets to get metadata from MusicBrainz, and it seems to write the same tags as Picard.

[epoupon]

We could imagine some fallback though. I opened a discussion here: https://community.metabrainz.org/t/multiple-album-artists/532302

[epoupon]

Well I have added support for some non standard tags that you can add using picard:

This leads to:

[ALBUMARTIST] = Burial + Blackdown
[ALBUMARTISTS] = Burial*SEP*Blackdown
[ALBUMARTISTSORT] = Burial + Blackdown
[ALBUMARTISTSSORT] = Burial*SEP*Blackdown
[MUSICBRAINZ_ALBUMARTISTID] = 9ddce51c-2b75-4b3e-ac8c-1db09e7c89c6*SEP*c583b756-a74d-4010-af7e-61482ab8aeaa

Interpreted as (sort name placed between ')

Album artist: Burial (9ddce51c-2b75-4b3e-ac8c-1db09e7c89c6) 'Burial'
Album artist: Blackdown (c583b756-a74d-4010-af7e-61482ab8aeaa) 'Blackdown'

Will now see if we can fallback on the " + " separator

[epoupon]

Now putting the album artists and make them clickable as the others (instead of just writing Various artists)

[abdulocracy]

Thank you for the great work. Off topic, if you plan to have a contribution method set up I'm sure I'd like to contribute with a regular donation. :)

[epoupon]

Ok, as this kind of collaboration can now be handled using tags, I am closing the issue.
Picard is considering adding albumartists by default for its 2.7 release. I don't know about beets.
Feel free to open another one/reopen if you have further needs!