OK, I'll weigh in here. It has been my experience that classically trained violinists can become quite good bluegrass and Irish fiddlers. The thing that seems to give them the most trouble is old time fiddling. With rare exceptions, they can't seem to get the "rhythm thing" going in old time, and their phraseology tends to be stiff and strained.

Then, separately, there is the issue of being able to learn a tune by ear. I propose that learning by ear uses a completely different part of the brain than learning from paper. I distinctly remember being shown a tune on paper, and being able to play it OK until the paper was removed. Then I could not play it AT ALL! Then I just listened to the others who were playing, picked up the sense of the tune, and then learned it quickly, but from scratch, as though the original attempt from paper had never happened. There was an odd sensation of my mind totally shifting gears. Now, maybe this is peculiar to me, maybe not. I would like to hear whether or not others here have had that experience.

Anyway, I think a person can learn both. But if learning from paper, you should just use it to get the sense of the tune, then throw away the paper, and doctor it up until it sounds good. The paper isn't the music. The music is the music. My two cents.

Al