Piano is a piece of cake. Art; now that is different. I don't mean to be mean here and all, but if you can't read an alto clef and can read everything else then you are really stupid or something. I mean movable clefs are the same as key signatures to most minds. Just make the adjustments in your mind.
Reading music , including sightreading, are all things that you can improve with dedication. Art is a feeling that can accept reciprocation, and that is something that a lot of people just don't have. Headlining a concert is just a damn good contract and a bit of luck.
It's determination. That's all.