'A 1950 recording of Horton Barker singing "Pretty Sally" is on Musical Traditions MTCD514/5 "When Cecil Left the Mountains...'

Indeed it is, Reinhard, and I really should have thought to mention it, since I'm right in the middle of writing an academic article about the trip made by Maud Karpeles and Sidney Robertson Cowell to the Appalachian mountains in 1950, from where the recording you mentioned came.