Actually, Diane, I think including Shirley Collins and Vashti Bunyan makes a great deal of sense. They both sing in a kind of weird, unusual, unexpected voice that instantly transports you somewhere else. In the Collins case, generally into a sort of mythical nymphs and shepherds kind of place, and with Bunyan more of a fairy, Celtic twilight, 60's Malory sort of thing.Of course, whether you wish to be transported into that world is another question.
Sandy Denny is a totally different kind of thing again. She sounds like a 60's/70's folkie. What it says on the tin.