Incidentally, Grahame, learning a jazz standard would not really be the same thing as learning a folk tune. We are not supposed to have "correct versions," and are supposed to be steeped in the spirit of the folk process. Not only can you not be that if you're reading from notation, you can't be that if you LEARNED the tune from notation (unless you've already spent years learning tunes by ear and know intimately the need for flexibility).

I might add, somewhat mischievously, that I could knock out my personal "expressive" rendering of "Summertime" for you right now on a blues harp. And I could repeat the exercise tomorrow morning and it wouldn't be the same...