"...invites audience participation and was altogether the consummate showman!"
True to an extent Paul, but one of the aspect of Sam's performance was that each time he sang the song, it was as if he was singing it for the first time - thaat is was a first-time-out experience.
I had a very spooky experience once when I visited a club with a friend I have always admired as one of the most skillful singers I have ever heard.
He sang a ballad I had heard him sing half a dozen times and it was literally stunning - it left me with a lump in my throat, is was so moving.
When I mentioned it to him on the way home, he said he was not happy with his performance - the song had so moved him emotionally that he thought he had lost technical control of it - he hadn't, but not the point.
I believe the secret of a good performance is to make the song work for yourself - if it works for you, it works for the listener.
As long as you have done your technical homework beforehand your listeners will follow you over a cliff.
Jim Carroll