"I don't think such songs could ever come into being via debasement; what we're seeing here is the product of a very deliberate and purposeful mastery."

What we may actually be seeing here (in the ballads especially) may be a glimpse of the creative workings of a non-literate culture (a culture that literate people, like us, can barely imagine). See David Buchan's 'The Ballad and the Folk'.