I should scan in some remarks I found in an intro in a spirituals songbook-- it talks about how the folk process refines the crap out of how the song was originally done, how it improves it by a sort of consensus of usage.

... which would mean that finding the original of a song would often not mean one had found it in its purest or highest form.

... and that the later forms are not degradations of the original.

~S~