Forbidden Symphonies

Duet (You may exile this spell as it resolves. If you
do, the next player in the turn order may cast this
card from exile without paying its mana cost at the
beginning of their next upkeep.)
Create a colorless artifact token named Thirsty
Harp with ''Whenever a player casts a spell they
don't own, they sacrifice a permanent for each
time this spell has been cast this game.'' Then,
draw a card for each time Forbidden Symphonies
has been cast this game.