I once heard a filk singer remark on her difficulty in remembering the recorded (frozen) version of her song "Green Eyes," as all the changes she had made remained in her mind. Another singer the night before had also mentioned that her song "changes every time she sings it."

The story, not just the words, evolved. A work ever in progress? Why not?

Then there's change to correct errors. For example, Wilf Carter recorded:
When I was a lad, Old Shep was a pup
Over hills and valleys we'd roam.
Just a boy and his dog, we were both full of fun.
We grew up together that way.

Surely the second line should have ended, "stray"? But I don't have other sources to compare, so I sing it the way I think it should have been. (No doubt I'd take more pains to check if I were singing in public.)

Maureen