Combinations of Composer as Artist, performer as composer, and all manner of things that make it impossible to search for multiple versions of the same piece.
That's where the concept of the 'canonical' title ('work' title) that MusicBrainz has available comes in handy.
If you have that written to the title tag, you can more easily achieve some uniformity in that.
That can also solve some issues with titles differing between album releases for different markets.
E.g. Das wohltemperierte Klavier vs. The Well-Tempered Clavier, Le quattro stagioni vs. The Four Seasons, Symphonie vs Sinfonie vs Sinfonia, etc. etc.
I have disabled Picard writing 'album artist'
Especially for classical music they often result in a very long-winded summary of composers, directors, performers.
I prefer them brief, and usually have them something like this:
Shostakovich (Previn, Mullova)
I haven't tried to automate that through scripting, because A. it's not a lot of work to do it by hand. B. In case there is no conductor, or his value for that album is not paramount (in my opinion), I will choose or add the 'main performer'.
That is subjective, and difficult to automate. (until machine-learning has reached the point it can do that for me)
Similar for album titles.
Beethoven, Bach et al. never came up with album titles, so I feel free to construct my own, short versions.
So for classical music I don't care much for accuracy or 'correctness' of tags such as Artist, Album, Album Artist.
Those are concepts that don't really resonate with classical music and it's compositions.
I try to keep them all short and simple, and only may have some purpose for them for occasional grouping or sorting.