For a start, his flatpicking guitar playing was pretty unique back then, but now there are thousands of players who play in that style.

Yes. He is why.

In answer to the original question, a good many times. From the Club 47 in Cambridge, MA in '64 - '67, to Williamstown, MA in the fall of '01, when Jack Lawrence, myself and my wife, and one or two other couples closed the Williams Inn bar after the concert.

Peter