The Lady Erskine plot is roughly parallel to the Greek myth of Phaedra and Hippolytus, even down to the use of horses.

To me it seems that the extreme derived from the mythic archetype is a different kind of extreme from the murder ballad based on a real event. These extremes (however you might categorize them, distinguish them, whatever) are supremely memorable; they stick in the mind and stick in the tradition.
Traditional Song= Where the Wild things are?

re the 'goof' of the Unquiet Grave,--the grove or grave or garden: when does print variation start to count like oral variation??