"if the audience came to see the Clancy,s they were telling the organisers they only wanted to see and hear them."
You seem to be wanting to have your cake and eat it here
On the one hand it's understandable that an audience can tell Jo they don't want him, but I should go to a pop open mike and sing what i want - while at th same time suggesting that I am being "unfieldly and unwelcoming" if someone turns up at my folk club with a Stradcaster and a sound system and plays 'That'll be the Day".
"would anyone know about these durable old warhorses had there not been a revival driven by a diligence of collectors working against the clock convinced of their imminent demise? "
No, but they would have existed for centuries, revival or not
" old tradition bearers giving up on the old songs overnight soon as they found something better to do"
The song tradition began to disappear with the advent of the Industrial revolution - there were still traces of it when Sharp declared it to be on the wane - the BBC were still finding a fair amount of it in the 1950s and Travellers were still making songs in the 1990s and possibly still are - hardly "as soon as...." - a bit unworthy of you Jack.
"Pop's durability is as an Idiom"
Pop = popular - the form in which it lasts varies from - how many months - years? - the individual songs - blink-of-an-eye and they're gone
Jim Carroll