> you start remembering words of songs you never knew.

Or imagining words of songs you did know:

"The animals came in cheek by jowl,
The gentle dove and the horny owl."

It popped in to my head the other day, but there's no way it could be in any version of "One more River" that I've ever met with.

Ought to be, of course.

Folk process: new words that pop into your head; see "chanteys."