Hello,
About this album:
https://musicbrainz.org/release/0521a4b0-69bc-470b-ad2c-d44d0ccbbf8c
Here is what I got in picard:
Regards,
Thatās intentional. The album artist of that album really is " Burial + Blackdown" (with + being the join phrase in MB). You can find the name of each album artist in the multivalued ~albumartists tag (should have the order as they appear in the artist credit). ~albumartists_sort provides the same as ~albumartists, but sorted by name. You can set the albumartist tag to just the list of artist names with a tagger script: $set(albumartist,$join(%_albumartists%,:,)) (replace : with the separator of your choice).
Thanks for your answer!
It looks like similar to the artist/artists tags, but I canāt see picard filling the albumartists tag? I can only see albumartist?
Does āI canāt seeā mean that youāre checking the metadata box at the bottom (whatās shown in your screenshot?). If so, then thatās - again - intentional 
All tags whose name begin with _ (~ in plugins) are not shown in that box and are not saved to files (more details in the docs).
You can view them if you install the āView script variablesā plugin, then right-click on a track, Plugins ā View Script Variables.
Ah, that explains why I canāt see these tags using taglib or ffprobe.
Well, do I really have to parse the : separator of the albumartist tag to extract both names? There is no standard way to expose multiple values for album artists?
Side note, I see this kodi recommendation: https://kodi.wiki/view/Music_tagging#albumartists
You can do what is recommended on that page:
$setmulti(albumartists,%_albumartists%)
Thatās exactly how youāll set a multi value albumartists tag.
Yes indeed, but why is it not done by default by Picard?
Picard already writes quite a lot of tags, I donāt think that adding yet another non-standard tag with very specific need is such a good idea. Thatās why Picard is configurable, to allow for such things.
You can open a ticket asking for this tag to be populated by default, explaining which apps are using it, and why it should be set by default.
As said, thatās a non-standard tag.
Well I wanted to open a ticket but I found this: https://tickets.metabrainz.org/browse/PICARD-700
and the related review https://github.com/metabrainz/picard/pull/553
Seems to be just closed/rejected.
What is the status on this?
Side question but related: do you know where I can find an official āgrammarā used by join phrases?
I see there are a lot of possible join phrases and quirks in Style/Artist Credits - MusicBrainz Wiki
All these join phrases make me think an āalbumartistsā tag should really be provided by picard by default
+1 for Picard writing āalbumartistsā by default.
To me itās an essential and very useful feature.
I guess no acceptable consensus was found by the time. You should ask in ticket.
@outsidecontext : what do you think?
No strong opinion really. I guess having albumartists would make it consistent with artists, and if there exists an actual use case with Kodi I guess it is only consequential to add this tag. As far as I remember Kodi was also one of the primary factors for artists.
We should have a migration to update existing scripts.
My only concern is that this could get kind of out of hands. Idonāt think Picard should add every imaginable information to tags by default. Unless there is a clear use case or common standard Iām more in favor to making the data available and let the users decide what to do with it.
But if someone wants to revert the change a script like this would do:
$setmulti(_albumartists,%albumartists%)
$delete(albumartists)
I personally do this for the artists tag.
Well I am about to instruct my own soft (https://github.com/epoupon/lms) to do the same as Kodi.
What annoys me most is that there is no easy fallback on parsing āalbumartistā to extract multiple artists since the MB join phrases do not seem to be standardized.
I do agree with you it could get out of control (maybe someone will ask to do the same for composers, remixers, mixers, producers, lyricists, etc.) but albumartists (and even albumartistssort) seems to be a reasonable minimum
That tag is used for display by players. If something is credited to āNeil Young with Crazy Horseā Iād like my player to show this, and not just a bookkeeping list of artist names 
If you prefer plain lists you already can set $set(albumartist,%_albumartists%). You can even set it to a multi-value tag with $setmulti(albumartist,%_albumartists%), if the player supports that.
Yes indeed, but ideally I want to make every artist clickable in this field, as it is displayed on MB 
Just curious, who for you is the albumartist for releases such as these?:
https://musicbrainz.org/release/3a2ae13b-0a81-40c5-b190-f9053100e3ef
https://musicbrainz.org/release/0a3dac0b-c058-4ae2-8ab9-4c329d650b61
I donāt know, Iām not familiar with any of those.