Steve: I found the Bell article via JSTOR. JSTOR is a free online source for many materials, including that one as it happens. Bell argues that Child was situated within a specific intellectual tradition which he discusses at tome length.

Jim: I agree that stuff can be 'co-written', as I have done this myself. Whatever the rights and wrongs of theorising about the matter, it seems to be a historical fact that there were strong disagreements about this aspect of the origins of ballads, and I do find the history of it all interesting.