Volumio has a “Sort Artists By” setting. It can be set to either “Album Artist” or “Artist”.
Despite the name suggesting otherwise, it doesn’t actually influence sorting. Instead, it determines from where Volumio acquires its lists of artists, i.e. these can be read from the artist or album-artist fields. For example, if the setting is set to album-artist, then lists of artists may include the artist “Various” (or whatever you use in the album-artist field to denote compilation albums), but it will not include any of the artists who perform only on compilation albums (as their names appear only in the artist field).
I’ve looked through the code and I just don’t understand what the point is:
 Why should Volumio ever read artists exclusively from the album-artist fields?
 Why must we specify what value we write to the album-artist field to designate compilation albums? No other player/tagger I’m aware of requires this. Why does Volumio?
Can anybody provide any insights? From a user’s perspective, what problems is Volumio solving with the above?