Wel am 28 and av been playing from the age of 15 ... I can't read any music and if you asked me to play a scale I wouldn't know where the hell to start lol but there's nothing I can't play ! I just need to hear a song and I pick it out and I always play the songs properly and miss nothing , my brothers the same , he plays guitar and together we play in a David bowie tribute band , so in my opinion you just need to have a good ear to be a good musician