I was there at that exact one. 85 live classical musicians on stage for the opening piece. This is very badly filmed and recorded, but it was 1977.
It's not showed in the video, but the whole orchestra came up from an wide elevator in the middle of the stage. Then a piccolo started playing the intro of Abaddon's Bolero to a full stadium of 65,000 people. It was like a mass, not a word, not a whisper.