I think the answer is this: "Album Artist" is (are) main person(s) behind album creation, but if there's the particular track with the guest performer(s) named Album Artist feat. Jane The Vocalist - Acoustic Rock Song, then in "Artist Name" field for that track goes Album Artist feat. Jane The Vocalist value while in "Album Artist" field goes Album Artist value.
1 Answer
Album artist is for the overall album artist, and artist is for the actual artist of the song. For example the first song on Sasha & Digweed's mix album Renaissance is Leftfield's "Song of Life" (I don't remember which mix). Album artist would be Sasha & Digweed, artist would be Leftfield.