Jinx is really fucking good at playing piano but he thinks it's a lame instrument to play unlike guitar or drums so he doesn't tell anyone. Though if he is in a bar and has had a few you bet your top dollar his ass is stumbling over to it with a 50/50 chance of playing actual bullshit or absolutely nailing it.

Ben also probably knows how to play piano; I imagine him playing the cello sometimes too. Not as fun as an answer because he doesn't really enjoy playing instruments unlike Jinx.