Most people of a certain age know that Richie Havens opened Woodstock. This was one of the high points. It's a very repetitive song. I've read that he played the long intro to create tension, to set up the importance of this song. He played from his heart like a man possessed.
Recently I heard an interview with Mr.Havens. He said the next act hadn't arrived, couldn't get through the throng, and they kept sending him back out on stage. He had only played little clubs and there were more people in front of him than he had ever seen. He was terrified. He said he was just a kid and he didn't have any more material. They told him to just play anything. So he went out and started playing. The reason for the long intro was he was trying to come up with words to sing. He felt like a motherless child because he didn't know what the next line was going to be. A classic, under pressure.