Hmmm, not about folk music, but my worst criticism ever was in several Choirs. The directors (a series of them over the years) always told me to be quieter and to blend in. Not just a bit, but several times each song of each rehearsal. From age 13 to age 16.

So now, I can't sing loudly at all. And I don't enjoy the sound of my voice even though I know in my head that it is beautiful.