$Group, $Sort(<Artist>) issue

[redwing]

If you filter with <Artist> using column/thumbnail browser, you get the artist's tracks in the main panel including those in which the artist is tagged as sub-artist like <Guest Artist>. But if you filter with <Sort Artist> for the same artist, you get only artist-tracks with sub-artist tracks excluded. It happens with $Group function too: all sub-artist tracks get excluded. I tried <Artists> tag as well, but got the same results when using $Group, $Sort functions. Is this intended or a bug?
As a background, I am using the two functions with artist tag in virtual tags to easily navigate artist names.

[psychoadept]

I ran into this a while back. When I thought it through, it makes sense.  Functions and virtual tags can only return one value, they don't deal with multiple values in tags.  And there can only be one Sort Artist value per track.

[redwing]

If that's the case, I think some special handling is needed at least for <Artists> tag.

[psychoadept]

It might be possible to manually enter more than one Sort Artist value per track?  I haven't tried.  But that's a lot of work.  I agree that a way to handle multiple Sort values for Artist would be helpful.  (At least in Artwork view, MB does apply the $Sort function to each individual artist.)

[redwing]

Did some tests, and it seems it could be achieved if Steven is willing to implement special handling for <Artists> tag regarding $Sort & $Group function.

Let me explain how this works.

Say, you have track X tagged with "AAA" for <artist>, "GGG" for <guest artist>, "AAA" for <display artist>.
And track Y is tagged with "AAA" for <artist>, "GGG" for <guest artist>, "AAA; GGG" for <display artist>.

If you filter with Artist, selecting GGG will show X and Y in the main panel.
If you filter with Sort Artist, then selecting GGG shows only Y (So our request is to show X as well here).

Then what's the difference between the two tracks? Both have the same tags, only display artist is different. So if MB reads, for $Sort(<Artists>), <Artists> tag value instead of <display artist> tag value (which is meant for $Sort(Artist)), then the problem will be solved.

As for $Group function, MB treats <display artist> tag value as a string rather than multiple tag values, and I understand it shouldn't output multiple values as this function is widely used for organizing files. Then how about outputting multiple values, for $Group(<Artists>), by grouping first xx letters from each artist, not from the whole display artist string?