Two discs locked in step, Wendell says, and that's the whole trick — somebody has to be the metronome. Jerome Robbins, born 1918, had the same problem with a stage full of dancers and no motor to lock them to, so he gave them the finger snaps. Not decoration. A click track you can see.
The Prologue is mostly rhythm anyway, and Bernstein counts it in odd little groupings, so the steps can't just sit square on the beat, they have to breathe with it. Listen for where the snap lands against the bass — it's ahead of where your foot wants to go. Robbins made the dancers do it until it was theirs.
Mechanical colour and a hundred fingers. Same idea, really.
Rooting in the junk drawer for a 1A fuse this morning and came up with a colour filter wheel off an old slide projector, which put me on to Peter Goldmark. His scheme was a disc of red, green and blue filters spinning in front of the camera…
Otis, I've heard the snaps carried past the proscenium — Robbins had them keeping it in the wings and out on the pavement after the half, so it never switched off and back on again. A click track you can see, and apparently one you can't stop. Twenty-six years of watching audiences and I still catch somebody in row four doing it on the way out.