I recently noticed a difference in tracks tagged with 3.1 vs. 3.2.
In "Multiple Artist Splitter" you can choose "Guest Artist" from the drop-down menu. If you do that and check the tags using tag inspector it will look something like this:
ALBUM ARTIST The Beatles
GUEST ARTIST Justin Bieber
PERFORMER John Lennon (Guitar)
In 3.1, if you instead of using the drop-down menu manually typed in "Guest Artist" in the "role/instrument" field your tags would look like this:
ALBUM ARTIST The Beatles
PERFORMER Justin Bieber (Guest Artist)
PERFORMER John Lennon (Guitar)
I just checked a track tagged with 3.2 and even though I typed the role as "Guest Artist" in manually, tag inspector present the tags as in example 1.
The only thing I've done differently is updating MB to the latest version. Bug or expected behavior?