Actually I did mean Bell Duncan of Lambhill, Aberdeenshire who was a major source of ballads for James Madison Carpenter. However I was quite wrong to suggest that Carpenter may have encouraged her to supplement her repertoire from the Child collection; instead he claimed that she "sang sixty-five Child ballads with tunes, never a single reference to manuscript". However he did have some doubts about some of her sources. Julia Bishop in her excellent essay 'Bell Duncan: 'The greatest ballad singer of all time'? in Ian Russell and David Atkinson (eds.) 'Folk Song: Tradition, Revival, and Re-Creation', Elphinstone Institute, Aberdeen, 2004, pp.393-421 examines Carpenter's claims.

Julia Bishop concluded that "Ballad books in particular appear to have been an important source both for [Bell Duncan] and for her mother and/or the other sources, direct and indirect, of her repertoire."

As far as Julia Bishop is concerned the use of printed sources at some stage in the transmission in no way compromises Bell Duncan's status as an important ballad singer, although in Carpenter's eyes and in terms of the scholarship of his era (1920's and 30's) this would have reduced her "authenticity".

The interplay between printed, manuscript and oral sources within folk tradition is fascinating and complex and I think Brian has raised an important point about how traditional singers recreated and reinvented their material. I personally would subscribe to the "grandfather's axe" view how of traditions evolve:-
"This is my grandfather's axe; I've given it a new blade, and my father gave it a new shaft, but it's still my grandfather's old axe."