"orchestra not playing"
I have for some time been under the impression that Billy sets the tempo at the start of Electricity, and the orchestra follows. Several videos show large gaps between lines.
I took notice in London and for the first time became aware the conductors box is actually a keyboard. When the Electricity started the conductor played the chord after Billy had commenced the line and conducted the orchestra with a downward move of his head. I am not sure how many play in the first section.
The keyboard plays one note to give Billy his pitch, and then Billy sings the first part alone before the music comes in.
In NY, there is a keyboardist in the orchestra. The conductor does not play the keyboard, as I recall. That is probably because in NY the orchestra is required to be twice the size of the one in London because of the musicians' union rules.