The Choreography of a Coincidence

I watched Grease out of

I watched Grease out of sheer boredom the other night...and noticed that during the song "These Magic Changes", the backup singers are actually singing the guitar chords. Seriously. They're saying, "G, G, G, A, A, A, A, F, F, F, F, G, G, G, G, 7, 7, 7," etc. You will notice that that's only 4 guitar chords to keep up with. And yet, they had to sing it to remember.