Ah yes, Karn Evil 9 definitely brings back fond memories of ELP. It was December of 1973, Brain Salad Surgery Tour, Chicago Amphitheater. They had set up the place with 4 towers of speakers for a "Quadraphonic" performance. We were seated in folding chairs on the main floor. The atmosphere was what you would have expected. At the end of Karn Evil 9, Part 3, when Emerson's synthesizer tones began and "chased" each other around the amphitheater quad setup, slowly picking up speed, I saw dozens of people around me becoming disorientated and dizzy, many just falling to the floor at the peak of the chase. It was TFA! A concert I will never forget.
Steve