I have seen sometimes that artists get mentioned more than once in the artist credits if it’s a medley or compilation.
E.g. “Song A / Song B / Song C (medley)” by Artist A / Artist A feat. Artist B / Artist A
Is that how it’s supposed to be (to know which part of the song Artist B is featured at) or is it sufficient to credit this track to “Artist A feat. Artist B” and then distinguish it further with medley & vocals relationships?
That is how it’s supposed to be according to the current style guidelines:
https://musicbrainz.org/doc/Style/Artist_Credits#Multiple_artists_.2F_Splits
There is no relationship to replace this information, at least for the time being.
The “Multiple artists / Splits” guideline doesn’t talk about tracks and recordings containing multiple songs by the same artist some of which feature additional artist.
I think it would be perfectly reasonable to credit the song in my example above as:
“Song A / Song B / Song C (medley)” by Artist A feat. Artist B
and in the relationship define it’s a medley of
Song A performed by Artist A
Song B performed by Artist A and Artist B
Song C performed by Artist A
The same artist some of which feature additional artist is a special case of different artists.
This special case is not treated differently in the guidelines. Maybe it should. But it isn’t.
There is no performance artist-work relationship type to replace this information.
Maybe a new relationship type or attribute has to be defined to that end.
At least it should be more clear. Because I don’t read the guideline the same way as you do, but if that is the intent of it then of course I’ll stick to it.
There is a compilation recording-recording relationship and there are performance relationships for recordings.
So you are right, this would only work for compilations, but not for medleys.