Once upon a time there was an oral tradition. In it the songs evolved because people developed or improvised bits if they couldn't remember exactly what was missing but instead came up with something they could live with. This usually took one of two forms. Either they made up rubbish which sounded like what they remembered hearing: so Queen Jane became our neighbour for six days or more, Sir Hugh found that it rained, it rained American corn, or Johnny Faa cast his grandma in the corner-o; alternatively, and most often, they came up with a sensible seamless correction which passed easily into the tradition. This was much of the charm, and much of the distinguishing quality, of folk music. Then the working class learned to read and everyone said that that tradition would die because the book version would become set in stone. But it didn't happen because even though some people learnt from books, and even though Harry Cox allegedly had a box of broadsides under his bed, no singer (except perhaps the Coppers) would think of taking the written text with them to the pub; and so they all made sure they had learnt their songs inside out before they tried singing them in public, and the adrenalin rush, if they did forget something, helped them use the same strategies as before. Then radio came in; and it was predicted the broadcast versions would drive out all variation; and when it failed to happen the same prognostication was made regarding records and tapes and CDs. And it didn't happen, for the same reason – at the point of performance, singers were still operating on their own. Then one day a folk singer walked into a club with the words of his songs, and used them to sing from. And noone told him to go away and not try again until he'd learnt the song thoroughly. And so every time he sang the song it was exactly the same.
And the tradition died.
And our generation killed it.