If you open the files with Tag Inspector in MB you will see they are both written as
Artist
Artist
Artist
No - see the original file
HERE and the converted file
HERE in tag inspector. MusicBee is splitting the tag on its own. I guess this is the best way I should have illustrated this issue in the first place.
A solution would be to use "Above & Beyond - Alex Vargas - Pierce Fulton" as your Artist Sort-Order tag and turn on the sync option to "replace artist tag with sort-artist"
That's an interesting workaround, thanks. But I'd rather not re-tag all my songs for this, even if it can be done in batch. I'd rather get MusicBee to stop splitting the tag. But, it's worth consideration as a workaround if this isn't fixed, thanks.
I'm not sure why the multiple artists aren't showing up for you in GMMP, but Bee-liever has a good workaround.
[Edit: one thing occurred to me that might make a difference, though I'm not sure why. I'm using Id3v2.4 tags. Are you using 2.4 or 2.3?]
In this case, MP4 tags actually. But I've seen this issue arise for both mp3 and FLAC as well.
For reference of anyone else coming across this post, here is a track with multiple artists in MB:
And here is the same track in Rocket Player and GMMP, respectively (synced by MusicBee):
http://i.imgur.com/cW8JL3Zl.png
http://i.imgur.com/lP7mBvPl.png
Weird. I have no idea why it works for you but not for me. In any event, that's an issue I can take up with the creators of the apps. The reason why I'm posting on here is that I am hoping there could be an option or a default where MusicBee doesn't mess with the artist tag during conversion. No idea how realistic that is, but it's worth a shot. I'm really surprised nobody else has come across this. I also notice it while tagging files. If I use Mp3tag to tag an artist in "artist1; artist2" format, and then later change a non-artist tag
within MusicBee (such as song title, album, etc.), MusicBee splits the artist tag on its own even if I didn't touch the artist tag. I realize it wants to use its own Multi-artist feature, but too many other platforms don't support multiple artists for me to want to use it.