Fascinating:

I decided to make it lyrical, thoroughly stylised: a film in which the whole action of actors, as well as the movement of camera and cutting was rhythmic. Then I got Rodgers and Hart to write the music?. We finished the whole score before I began to work on the script. We did the whole thing to a metronome, because we couldn’t carry an orchestra round with us.
-Rouben Mamoulian (director)

I’m a great believer in conversational rhythm. I think in terms of rhythmic dialogue. It’s so easy, you can talk naturally. It’s like peas rolling off a knife. Take the great screen actors and actresses, Bette Davis, Eddie Robinson, Jimmy Cagney, Spencer Tracy. They all talk in rhythm. And rhythm and movement are the life of the screen.
-Lorenz Hart (lyricist)

Princess: Then why do I lie awake in bed? And why does the blood rush to my head?

Doctor: At night?

Princess: Quite right. At night. And why does music make me so sad? And why do love songs drive me mad?

Doctor: At night?

Princess: Quite right.

-from Love Me Tonight

(I found this here.)
—–