I am a guitar player. Have been for a long time (better than 30 years now). I started with some lessons from a fellow BBS’er Vernon Anderson (He ran the”Rat’s Nest” BBS).
I learned a lot very fast. I do remember the basics of music theory. How to build the scales, all the modes, the circle of 5ths, intervals, etc. But it really didn’t stick. I was too impatient to learn to play cool music, and the theory was boring to me. So I learned Scorpions, Aerosmith, Led Zeppelin, and other great tunes. I got pretty good at just riffing on Em pentatonic (if you can’t play the shit out of E pentatonic minor, you should give up the ‘axe), and playing bluesy licks and riffs.
Then I stalled. I practiced a lot when I was in college (it was a good excuse to not study), built some speed and chops. Even played out a few times. I picked up Noad’s Beginning guitar and learned some classical pieces (and how to read music).
Fast forward 20+ years. I have been playing more, and picking up my skills again, but I am finally beginning to dive into theory. It is hard, because it is so tempting to just rip away. But I know that if I stick with the theory, the rest of my playing will become much better (and I will fumble less for notes when I am soloing.)