Select ACTION, then create a new action (upper right hand "star" icon). Give your action a name (e.g., create album artist), then in the next box, click the upper right side "star" icon to create the action. It will ask you for type. use the drop down box to select FORMAT VALUE. Within this select the field (in your case ALBUM ARTIST) then enter the format string (in your case %artist%). Then save this. You might want to add a second action at the same time to put %artist% into ALBUMARTIST (note no space....some apps use this instead...and it doesn't hurt to have both tags).
Now you have an action. select a music file and select convert, then action, then run the action on the file. Then SAVE. You should see that the album artist field now has the artist filled in. You can select 1000s of files at once to run the action on (test it on a few first). I've noticed that I sometimes have to run it on batches of 8 or 9 thousand tracks. I think my computer memory limits me a little. I know I've had some actions choke when I tried to run them on 80,000 files at once.
Get comfortable with the ACTIONS functions of mp3tag. This is where most of the power is!
agree. so in his action, he should also format value (BAND) with %artist%. Actually, in my case, I cause BAND, ALBUM ARTIST, and ALBUMARTIST to all take on the same value, so I'm good in foobar, itunes, squeezecenter, etc.
Unfortunately, the problem will arise with a lot of albums. The various artists, of course, but also any album with at least one track by another performer, be it the "album artist feat. Somebody", or the odd bonus solo track by the band leader, or the MC introduction on an old live album, etc. Lots of cases, actually, and I don't think this could be scripted.
I'm using Foobar and so I don't know well MediaMonkey but I guess the "View by artist" can be changed to the artist tag instead of the album artist tag. Or maybe the performer tag, in which case it would be easy to copy every "artist" field to the "performer" field, without splitting a lot of albums.