Aeola, that's a very interesting point you've raised. There are, of course, thousands of songs that don't survive. Many vanish without leaving a trace, but others can be found in books and manuscripts. Scholars of folk song sometimes trawl the archives for long-forgotten gems; sometimes they find a real jewel of a song that merits being reintroduced to the repertoire, but in other cases there's clearly a reason why the song remained forgotten for so long ...

For example I've got a 1970s book called One Hundred Songs of Toil.
Many of the older songs in it are still regarded as classic, but there are also some modern ones in the collection. Most of these have not survived, as far as I'm aware, although they may have served a specific purpose at one time. At the time of publication, these new songs had not been subjected to the "folk" selection process, and many of them are simply not good enough to stand on their own merits 40 years later.

Marje