Steve
In which case we have to find a defining feature between 'A 'Metamorphosis on Tobacco', 'London Ordinary', 'Banks of Sweet Dundee', and 'Little Grey Home in the West' - all of which have appeared on broadsides, and are therefore 'ballads'.
If we can't, the term becomes meaningless and the question "what is a ballad" unanswerable.
Jim Carroll