Well, whatever you want to learn it is a very big field with music theory.
Sang "Rudolph the Red-Nosed Reindeer" when I was three, and played drums and accordian when I was four.
I think I have forgotten more than I learned. And still probably may yet learn more or not.

Back to my man-cave to eat snails and puppy dog tails and dress in blue, I guess.
I also have an ex-wife (and I may be dead as of then which was a while back now).