There is a Greek legend about King Midas who was clearly a man who had problems with magic. Not only was he given the golden touch, but over some dispute over musical differences with Apollo, grew Donkey's ears.
Only his barber knew the truth, and whispered the fact to the reeds, which were made into Panpipes which did the magical outing trick, just like the macabre fiddle/harp or drum above.
Somewhere in my library I have an account of a social-psychological study of rumour. It describes how, when people remember a story and re-tell it, it is as if they remember the key points, then re-build the narrative to connect them.
-Really wierd details like talking fiddles tend to survive unless cultural inhibitions, such as religious doctrines, suppress them.
-Anything which, from memory, appears to be unconnected- for example the callousness of the Miller, is either taken out or rationalised- he stole her ring.
-Interesting fragments of other stories are often grafted on. Legends about Sir Francis Drake often include borrowings from tales of Bran the Blessed and King Arthur- Drakes Drum and England's time of need for example.
My interpretation is that there is fundamentally one song, but it is localised by the singer to bring it closer to his or her audience. In a similar way, if I tell the "Phantom Hitch Hiker", I always start by describing a suitable local road on which it is alleged to happen.
It's just the folk process in prose!
Cheers
Dave