I have had one "official" (i.e., paid-for) music lesson in my life. But I used to live near Dupont Circle, in 1966-1967. During the summer season (whenever it was warm enough and not raining, that is, no matter the month) there were always little knots of people gathered here and there on the grass, playing music. Usually whatever was going around in "folk circles," but that means it was pretty eclectic. And anyone could sit down in the circle, open an instrument case, and play along as best he/she could. And the good thing was, when the song was finished, you could ask, "Hey, what was that where you moved that D chord up the neck?" and get the answer, "Oh, well, at the 7th fret, it's a G chord, and up at the 9th, you get an A. You have to watch the bass strings, but it works." Bingo! Instant lesson in chord inversion (or alternate positions, whatever you want to call it).
I must have had as many as three or four such lessons every night, for two summers (by 1968, it had gotten pretty hairy there, and it's hard to play music while breathing tear gas). How many lessons is that? Add to it places like the Alexandria Folklore Center, in operation at the time, where similar learning sessions could be carried out, and I had a bachelors/masters/doctorate season in two years.
In that time, I took up banjo, mandolin, autoharp, and fiddle, plus making much improvement on guitar and even harmonica. I had my first public performances then, which is a totally different kind of learning experience, but a valuable one. I wrote my first Gawd-awful songs, too, just to show that that time wasn't a total plus.
So am I a trained musician?
Damned right I am.