MB treats "PERFORMER" at the top level of the cuesheet as the album artist but the file tags take precedence, except for track specific tags such as artist, track number, etc
To set the artist for each track do something like this:
TITLE "Symphonie no. 25 KV183 (g)"
FILE "M25.m4a" M4A
PERFORMER "hr-Sinfonieorchester; François Leleux (dir.)"
REM YEAR "2017"
TRACK 1 AUDIO
TITLE "1. Allegro con brio"
PERFORMER "artist1"
INDEX 01 00:35:00
TRACK 2 AUDIO
TITLE "2. Andante"
PERFORMER "artist2"
INDEX 01 08:32:00
TRACK 3 AUDIO
TITLE "3. Menuetto, Trio, Menuetto"
PERFORMER "artist1"
INDEX 01 12:04:00
TRACK 4 AUDIO
TITLE "4. Allegro"
INDEX 01 15:35:00
TRACK 5 AUDIO
TITLE "Bravo"
INDEX 01 21:47:25
you will need to right click/ Send To/ Rescan Files so the cuesheet is reloaded