Just to be clear, the album artist is correct for MusicBrainz. That is their style guideline. TBH, I don’t care so much that, philosophically, it’s wrong, but that the treatment in their database is consistent.
“Correct for MusicBrainz” sounds to me like “Normal for Norfolk”. 
With a collection groomed towards Rovi’s much more logical and consistent metadata, having the odd Musicbrainz model mixed in makes chaos and turns Roon’s careful structure upside down.
Anyway, here’s the link to the Rovi metadata:
So to identify with the Rovi metadata, you need:
Artist = Alfred Brendel
Album = Schubert: Forellenquintett; Mozart: Piano Quartet
@Mike_O_Neill We know there are issues and inconsistencies, and we are working behind the scenes to make it substantially better.
Strangely I have now managed to identify it.
The file tag Composer and Artist will be correct in the file, I always use the tags as per their names
Thanks for the help.
Mike
Sorry to nag, just one last question
Is it possible to “Merge”. Individual compostion line items into true Composition when all else fails
I see there is an “unmerge” but I can’t find Merge
Mike