s&r: "As soon as you try to make music. When do you become a good musician is a different question.

Stu"

Well said, Stu.

I find it interesting that I can call myself a "figure skater," "gardener," "songwriter," "singer," "guitar player," "parodist," "folk dancer," "teacher," "researcher," and any of a whole slew of words that describe THINGS I DO (some professionally, some as an amateur) and nobody bats an eye.   I don't seem to be required to be "accomplished" or "expert" at any of those things for it to be accepted by people. But I seldom refer to myself as a "musician" (despite having some formal training in violin, piano, choral music, etc.), and that's probably because of the way many people use that term.
E.g., in some circles, "musician" means "instrumentalist" -- not rhythm guitarist or drummer or vocalist, but instrumentalists who play lead or who play music with no vocals at all. Some people even add the criterion that you've got to be a GOOD instrumentalist before you're called a "musician."

This doesn't seem fair or logical to me, but I think it's reality.