we need to sum up what we already have. So do it.

Roud's book isn't academic. If it was the rules would have required him to go back through 120 years or so of other people's ideas in tedious detail. He starts at the other end of the story and methodically presents historical information about what the folk were singing. His evidence suggests to me that the folk have always done what folk who make their own entertainment do now. But more often because most of the time there were no professional entertainers to be entertained by.