"And does a song stop becoming a folk song once it is collected and that transference ceases?"

Why do you assume that collecting a song stops the process of transference? Folklorists have understood for decades that there is a reciprocal relationship between oral transmission and print. Likewise, American scholars such as D.K. Wilgus, Archie Green and Norm Cohen have demonstrated the role of recordings in transmitting songs. A.P. Carter collected songs from 'folk' sources, revised, rewrote and recorded those songs as commercial 'pop songs' and, through the much-maligned (by some, anyway) marketplace, sent those songs right back to the Folk (folks) who had been singing them for years.

Why the 'Either/Or contruct', Sinister Supporter?