"But I agree that I can think of few Shirley Collins soundalikes."
I'm talking specifically about the use of head-voice, noted by Bert Lloyd when he made his "bucolic" comment as being fairly rare in folk song, but later producing many imitators of the style.
I'm not denigrating head voice - extremely attractive when used well (and sparingly), but it raises problems which have to be noticed and need to be dealt with.
Jim Carroll