"Asserting anything else is an insult to our forebearers" (PoppaGator)...how about some respect for the collectors, many of whom would have been classically-trained and quite capable of notating more than one line of melody - if that's what they had heard/recorded, rather than a single-line of playing/singing.
Also, somewhere in among my myspace Friends (?after 5000, we can't do internal searches) is a post-grad. folk-degree student from one of the Scandinavian countries (Norway, I think), who said on her blurb that their tradition was a soloistic one of unaccompanied singing.