nice art, every game could use a monkey character, ability concepts are a little too similar effect wise for my taste tho.
What the The Pop worked as a channel ability, with the longer it is cast, the higher the dmg. But it'd slow you the longer the music is player.
Same thing for The Weasel, getting stunned/silenced would interrupt both and put either on cooldown.
Organ Grinder also being a dmging spell feels a little redundant, what if organ grinder was more of a utility spell? Jojo grinds his own mechanical organs, damaging himself and speeding himself up for a duration, while leaving behind him an oil trail that would slow enemies movement speed and firing speed.
Fortissimo's pretty good!
Finally, this is less than an actual suggestion and more nitpicking than anything, but being able to cast the abilities and shoot at the same time sounds pretty powerful, so I'd put it behind an upgrade, probably Fortissimo's 3rd upgrade