The consert was not at Olympen, it was at Stora Salen AF. Olympen was not built 1967. I was at the consert. Zappa did not bring any PA system for the singing, they tried to use the PA system in Stora Salen but it was construckted for speach. So they soon gave up the singing. There was actually two conserts that evening, but it turned into one long jam session without singing, with a change of listeners in the midddle. I was able to attend both sessions. It was a smashing success!