Jag>>>>>> to allow something that most people could remember and join in with<<<<<< It did happen but not that often. Check out 'Johnny Sands' Laws Q3, Roud 184 which is a Music Hall rewrite of the earlier piece 'Marrow Bones', Laws Q2, Roud 183.(both found in oral tradition).

Also the broadside ballad 'William and Dinah' was parodied by Henry Mayhew to become 'Villikins & Dinah' (both found in oral tradition).

William Taylor, another example, from a 50 verse mid 18th century garland version cut down by the broadside writers more than once to about 12 verses, then that burlesqued for the Music Hall and then several of these running parallel in oral tradition, the burlesque even reverting to serious song.