Lyric discussion by jaemie22 

Cover art for Not Today lyrics by Twenty One Pilots

"Don't you test me, no, just because I play the piano doesn't mean I am not willing to take you down, I'm sorry."

So many people seem confused about this line, but I think, like, possibly, he's saying that people see him as weak, because he plays the piano, because it's a softer instrument. Maybe being weak is an insecurity to him, or that line is for his fans. But then he lashes out and says he isn't weak, and he can still fight for himself. He then says sorry cause he is actually a soft person, he doesn't like being mean to other people, even when they do him wrong, that's what I thought.