They're different in all sorts of ways; certainly different enough to be compelling. It's a bit like in evolutionary theory really saying that a town fox and a city fox aren't as obviously different as an Indian elephant and an African elephant. Big differences are the results of little differences and the minute increments of organic process which is everywhere. All is change; all is changing...

The TFP-hypothesis is oft expressed thus on Mudcat; soon as it crops up again I'll be sure to alert you. Actually, I quite like the more random elements of the theory, as well as the creative ones. In short, I suppose, my beef here is as much with the nomenclature as anything else when such process is universal and not restricted to Folk Music. After all, Mondegreens do happen and do lead to some some great variations.