"However, Lloyd here acknowledges that he's sometimes altered tunes and texts "deliberately"
Ballad scholar, David Buchan once put forward a theory (contested by some) that, as far as the ballads were concerned, there were no fixed texts, just a basic plot and commonplaces (lily-white hand, milk white steed, etc.) - he suggested that, rather than memorise a set text, the singer would use these to perform the ballad.
It's a fascinating idea - if it's true; personally I've never been sure, and Buchan failed to produce enough evidence to convince (see; 'The Ballad and the Folk' (R&KP 1972).
I do know that with some of the big narrative singers, such as blind Mary Delaney ('From Puck to Appleby'- Musical Traditions), she often sang the same song differently.
One of the most spectacular examples of tune alteration I ever heard was from wonderful Seán Nós singer, Tom Costello (Tom Pháidín Tom) singing 'The Grand Conversation on Napoleon' which can be heard on Volume 8 of Voice of the People, ('A Story I'm About to Tell').
According to Terry Yarnell, who recorded Tom, he always used the shape of the tune as a base, but he never sang it the same way twice.
The tunes to the songs with some older singers were movable (and sometimes immovable feasts) - we recorded a couple of elderly brothers her in Clare with about fifteen songs between them, about six of them were to the same tune.
Tunes were considered by singers as vehicles to carry the story, of secondary importance.
Bert's 'crime' was not that he altered the texts or tunes, but that, on occasion he made academic assumptions based on his own alterations.
Jim Carroll