Q: if im learning a song on GarageBand piano, and im listening to the song as reference, how to i simplify what im playing so i dont end up playing as many notes as im hearing
A: this is really an artistic exercise, which is actually pretty fun and easy. at each moment, play a game where you ask yourself 'what would i do if i HAD to express this harmonic moment in just 1 note.' and i think you can pretty clearly find an answer. and then just move it up to 2 notes and leave it at that. maybe use 3 in an emergency