The one I still remember was year? Ready Steady Go, late at night, sat up alone. You have to remember RSG was a POP music Programme. Manfred Mann (a pop group) came on and Paul Jones sang Dillon's "With God on Our Side" at the end there was total SILENCE throughout the entire audience, me too, for about 10 seconds before the whole place just erupted in applause.
I still have to thank Steeleye Span for breaking the Irish trap and showing me the Trad English Light.
Jennifer Warnes sends the shivers down my spine too.
And Davy Graham, Bert Jansch, John Renbourne, Nic Jones, Martin Simpson, to name a few guitarists.
JohnB