I guess my two favorites of occasional collaboration were
Chet Atkins and Mark Knopfler
The Travelling Wilburys.
Weve Posted these bfore so Ill not dig m up gain.
Non Rock (kinda Spyrogyra stuff) would be
Ry Cooder and VM Bhatt "A meeting by the River"
Jazz? Im not a collector of a few, Im a jazz omnivore. I keep it in my studio allday. Most pf the really gret stuff is solo (like Take 5) and "covers" (Like Jimmy Smith )
Classical, Baroque, and Romantic. I like to hear the notes as written. Maybe a little Bach or Vivaldi "Jazz" the rest needs to be played as a great interpretation and while their are some really great "Sit ins" , I dont consier them real collaborations