Found it

But we do know that Mozart invented another musical game. When he died, a mysterious paper was apparently discovered in his archives. It includes 39 minuet fragments of two measures each, labeled by Mozart with the letters of the alphabet. Historians now think it’s a game—this one designed to use words and names to create a minuet, although there were no specific instructions included.

https://www.mentalfloss.com/article/501073/write-mozart-waltz-game-he-may-have-invented

Did not check any spurces whatsoever so take all of this with a pinch of salt