The musicians' pets are upset because their masters always dump them at the corner when they play music together. To please their masters, they decide to form a band and create some nice music, which they think will attract their masters' attention.
However, the pets have only a smidgen of musical knowledge from looking at their masters' practices — five lines, notes, basic beats, etc. — so they find it very difficult to compose music. Therefore they decide to start from the simplest point and use their masters' instruments to make a piece of music. And they name the band following the great musician Mozart as "MONZART"! After all, the pets are animals, so they cannot control their temper properly and sometimes just release their temper for no reason.
During Monzart, players act as one of the pets, trying to use their hand cards to place as many music notes in clef as they can to score points from the notes and the combinations of notes. If you found yourself in a hard position, don't worry! You are a pet and are allowed to release your temper! You could be angry, or you could be upset! Either way, you can use this reason to override your situation!
At the end of the game, whoever has the most points — from the game itself plus the final number of the notes — can attract the masters' attention as the "Best Composing Pet"!