When I looked at extended tags in MP3tag, it looked like MC was overwriting BAND with the ALBUM ARTIST, but looking closer, I now see that there is another BAND tag. It shows as JR/BAND in MP3tag. I don't think SC is reading this one, but it seems to be working the same as before in SqueezeCenter. (I had to wait until it did a full rescan overnight before I knew for sure.)
The way I use it is for artists like:
Rob Thomas / Matchbox Twenty
Ian Anderson / Jethro Tull
Tom Petty / Tom Petty & the Heartbreakers
I have it set up so that when I choose the soloist from the artist list in SC, it shows me all the solo albums AND the band albums. When I choose the band name from the artists list in SC, it shows me only the band albums.
I do this by making the Artist whatever is on the spine of the CD case, the album artist is the soloist, and Band is the band (if applicable). Then I set SC to show bands in the artist list and all is well. So for the Rob Thomas example, I would tag a solo albums as:
Artist: Rob Thomas
Album Artist: Rob Thomas
Band: <empty>
and a Matchbox Twenty album as:
Artist: Matchbox Twenty
Album Artist: Rob Thomas
Band: Matchbox Twenty
Since the change to MC13, Squeezecenter now shows this for a Matchbox Twenty album:
Album Artist: Rob Thomas
Band/Orchestra: Rob Thomas
Track Artist: Matchbox Twenty
With MC12, SC showed this:
Album Artist: Rob Thomas
Band/Orchestra: Matchbox Twenty
Track Artist: Matchbox Twenty
I don't really like seeing Rob Thomas listed as the band, but as far as browsing the artist list, it works the way I want it to and I guess I can live with it. I will play around with some SC settings on a subset of my library to see if I can get it any better. There is a setting:
Treat TPE2 MP3 tag as Band
Treat TPE2 MP3 tag as Album Artist
...that I can try changing. Currently I have the first option ticked.
Other suggestions welcome. Thanks for your explanation.