Very interesting responses.In retrospect I should have titled the thread
"What is the folk process?" Steve Gardham makes the very valid points
that accident and artistic improvisation both had a role. This neatly provides the distinction, in my mind, between the "purity" of story telling where the essential core element has continuity through the generations although the extraneous detail of the narrative could be given a little artistic improvisation, as opposed to song where both tune and lyrics could be given a massage without any harm. I would argue story telling often contained a core that required integrity of transmission, whereas song was a more "relaxed" medium where the essential message allowed more leeway in transmission. The two served different objectives of bard and minstrel(to put it crudely)