I not only attended this gig but I met Simon and Garfunkel afterwards.
Apart from the obvious joy of hearing their songs live, the specific details I remember from the show include Paul re-stringing and re-tuning his guitar in the middle of a song when a string broke. He didn´t stop playing. A roadie rushed on with a string and slotted it in while Paul continued to play, tuning up as he went.
Art Garfunkel doing For Emily Wherever I May Find Her was also a bit of a show-stopper. Single spotlight picking him out at the front of the stage, and that gorgeous, angelic voice soaring around the Usher Hall.
After the show my friends and I hung around outside until after half an hour or so, Simon and Garfunkel both came out, looking for the car that was to take them on to the next gig.
As I remember it, we sat on the side steps of the Usher Hall and chatted to them for maybe ten minutes - very star-struck. They seemed worn out, told us they were deeply unimpressed by British roads, and behaved almost like battle-hardened war veterans, determined just to keep going until the tour was over and they could go home.
Neither of them was exactly chatty, but Paul was more friendly by some way than Art, who seemed very distant and aloof.
Thinking back, it´s interesting that I never doubted I´d get to meet them if I hung around. There was no security to keep fans away from the artists, just two young men travelling from town to town under their own steam.