I have heard some of the less than polished and non-professional English singers described (or dismissed) as being source singers.

Being described as a source singer in such a way - rather than simply acknowledging a named individual singer as being the source of the song (or at least where you may have first heard it) - is perhaps the cause of any reservations about the use of the term - source singer?

It may be thought to be a subtle difference but I suggest it is an important one.

There is perhaps an element of snobbery involved in this pursuit of the 'real thing' The recent Folk Brittania show was interesting in this regard. I am not sure if she ever claimed to be, but Margaret Barry was with some reverence, thought by many to be the 'source' of She Moves Through The Fair. When her source was in fact a recorded version.