>>>>>>Is there a term for the subset of 'what the folk sang' (and of what falls within the 1954 definition and what as revived in the post 1950 folk clubs) that has been the centre of discussion in this thread?<<<<<<

jag,

You have identified in this question one of the much-discussed bones of contention. Terminology for our genre is rife with difficulties. Part of the problem is that some people don't want to accept that most words in the English language have multiple meanings/definitions and 'folk song' is no exception. In fact like the language itself the meaning of 'folk song' is continuing to evolve. All 3 of your subgenres can and do use the words 'folk song' to describe them. Most of us are happy to use the words to describe all 3 and use extra adjectives to narrow things down, such as 'contemporary song' 'traditional song'. This has been discussed and argued on many threads and again will continue to be so.