Well, maybe, Suibhne, but what Jim seemed to be implying (to my mind) was that it was essential to listen to the source singers to appreciate the songs in a modern context. Bit like saying you can't appreciate Shakespeare's King Lear without reading Geoffrey of Monmouth's History of the Kings of Britain or Lord of the Rings without reading Beowulf, The Kalevala and the Mabinogion.

I'm in no way denegrating the source singers, just questioning their actual influence on most people's enjoyment of the music.