Cap'n,
I'm sorry, I can't follow your question at all.
Of course the Radio Ballads were for anybody who would listen to them, but in realistic terms the audience they got was mainly the one that was also keyed into traditional song and, hopefully, some of the people from the communities dealt with, (miners, Travellers,etc) or those who had a particular interest in those communities.
This has nothing whatever to do with the subject in hand - that of defining folk-song.
Every Traditional singer we have met has increased their repertoire in some way or another, quite often the reason for this has been that our interest has prompted them to dig into their memories for half remembered songs and re-construct them. Fred Jordan had a number of songs he learned from new in order to build his repertoire for club performances.
Walter first heard his family's songs as a child, at harvest suppers or at Christmas parties. He filled gaps in songs from books (occasionally he had only ever known a few verses of some, (in some cases, so had his sources - his uncles or his parents). The only song he learned completely from new was 'Topman and The Afterguard' because he believed the version he heard in the army was too 'obscene' to sing in public.
A traditional singer is, as far as I'm concerned, somebody who has come from a background where the tradition was active, a revivalist is a singer who has taken the songs up as an outsider ( a bit simplistic, but it'll do for this hour of the morning.
Jim Carroll