OK..one amateur lecture.

In Child's day, it was quite a feat to find and organize all these at all, what with few other scholars helping, and no internet to look up other opinions. (Only 'slightly' tongue in cheek there.) Lots of elements and lines appear in other ballads.

Many of the songs and stories are about legends and myths, and it's a hard task to decide what is a different story, and what is simply a different version of a story. There are several of the ballads where the debate still rages about whether it deserves a separate listing, but Child's list is pretty good and quite 'set' in printed editions, so singers & scholars who care just try to be aware of the relationships & similarities.

If you look at the table of contents in Child, you see some basic grouping of the ballads by age, then, it seems to me, by subject. (Robin Hood is one example)

As soon as we have clarified the precise meaning of 'folk', I propose we sit down and revise Child, adding ballads he missed and re-ordering them by ....let me think....