When I was in high school, I picked up some accordion and guitar skills on my own without learning sheet music. I put together some folk dancing composition and was presented to perform it by concert organizers. I clearly was NOT ready and my practicing were going literally nowhere. I was able to get most of it right, but wasn't able to sound correct and at higher speeds would certainly trip even on well brushed-out pieces, but on stage -- it's all so different and I was backed up fo sho!
I'm 99% sure that most of the pop bands backed up by pros including pop singers.
To tell you the truth uptill now I can't get it right and my accordion is SOLD.