The big ballads often state their origin explicitly. They are frequently glorifications of aristocratic thuggery - we know of some songwriters among the gentry themselves, but it seems more likely that they paid their more literate retainers to write for them, in the same way that many lairds had their own musicians (where music was often only one of their jobs, as with William Marshall's employment by the Gordons of Huntly). Why would any farmworker want to write a song praising his master for fighting a feud? (Sometimes the power of the elite is treated as a problematic matter, as when the heroine of "Lord Gregory" ends up pointlessly dead; Kipling followed the same path when writing about how the British in colonial India fucked things up for themselves - but Lord Gregory" is not a call for revolt against the patriarchy any more than Kipling's descriptions of disastrous marriages were).

A really interesting treatment of the way elite ideas get circulated and transformed in non-elite cultures is the work of Carlo Ginzburg, in "The Cheese and the Worms" and "Ecstasies". The relationships are not at all simple, but you can get definite answers about where intangible cultural artifacts came from.