Glad to hear it's coming together. Do you use the term 'oecotypes/oikotypes'? This is usually where a new song made up from another or others has its own autonomy and has spread orally in the new recognisable form. The obvious example is 'Streets of Laredo' and also I suppose 'The Butcher Boy'. They are much more common your side of the pond but they can be identified over here as well. There are plenty of examples in Greig-Duncan as much rewriting went on in Scotland in the period between 1780 and 1820.

I keep meaning to be helpful but what with other distractions (projects and family) and the fact that you move so fast it's hard to keep up with you.