Cass Elliot said this in a 1968 Interview with Rolling Stone Magazine...
It’s true, I did get hit on the head by a pipe that fell down and my range was increased by three notes. They were tearing this club apart in the islands, revamping it, putting in a dance floor. Workmen dropped a thin metal plumbing pipe and it hit me on the head and knocked me to the ground. I had a concussion and went to the hospital. I had a bad headache for about two weeks and all of a sudden I was singing higher. It’s true. Honest to God.