I filled in Album Artist manually this weekend, so I discovered how it works.
I'm not in a position to post a screenshot of it at this time, which would save a lot of explaining, but why I want to is this: I have a bunch of compilations and soundtracks. I do not want the Artist tree to go into infinity because it makes an Artist node for every single song that has a different artist. I've tried this in the past, and that's what it does. I want a tree that shows basically the artists I'm truly collecting, and keep those compilation discs under 'Various Artists'...as I said. That way I can viewscheme using 'Album Artist' and the tree will be much shorter and more accurate because there will be a boatload of compilation discs kept under 'Various Artists'.
The way you've got it working now, it's like so: Imagine you've got one CD by Lunatic Calm. You also own the Matrix soundtrack. Lunatic Calm appears on the Matrix soundtrack. In the Matrix soundtrack you've defined Album Artist as 'Various Artists', and you've defined the Artist for each individual song properly, including the one by Lunatic Calm.
So: view by Artist/Album. What do you see under Lunatic Calm? Just the one CD and not the second entry for the Matrix soundtrack, because the 'Various Artists' entry you put in Album Artist is now overriding the display of what MJ considers to be the Artist. Thus, if you wanted to use your Artist field and viewscheme to view all individual CDs that have tracks by an artist no matter where they appear across your whole collection, you can't do it unless you abandon the use of Album Artist to help group compilations using 'Various Artist' or what have you. If, in this example, the Matrix soundtrack had no entries under Album Artist, then the tree would display both CD's under Lunatic Calm's entry.
When you've got both of these fields filled out, one overrides the other, which makes it pretty much without a whole lot of value, as MJ is currently implementing the display of it. Can we get this changed? Break the relationship between Album Artist and Artist. Just have it be like any other field. If there's no entry in it, it's unassigned; don't substitute one or prioritize one over the other.