I saw them live on Feb 21st, 1974 and it was an amazing memorable event. I recognized sound system designer Bill Hough standing by the mixing desk looking at the stage. Despite my only being 14, he did speak to me for a few minutes. He mentioned digital delay lines as something very new they were using. Bill also mentioned that "a Scully Metrotec 24 track is backstage to take down every show." Back Door (ptoduced by Carl Palmer) opened the show.
I've got to say that I think it's very cool that a fourteen year old kid would recognize a sound system designer. Props to the young you!