I learned to play guitar as a kid, played some classical and jazz as a teenager and in my twenties, then put it down. I have a nice classical guitar sitting in my closet for a decade.

My problem is that although I can read music, understand some theory, can play chords and even some can play a little bit of complex music like Villa Lobos, I have absolutely no "ear". I can't even tune the guitar without help.

So this means I basically need to memorize or play from sheet music, which kind of got boring after a while.