Oscar Castro-Neves is an accomplished guitarist and composer. He writes musical scores for movies. He says it is common in a dramatic scene to gradually bring the music to crescendo, and then stop--rest--silence. "Whatever is spoken on the screen in that silence is heard more clearly, more powerfully; the words are lent an additional potency, because they are spoken out of the silence. When you listen to music," he counsels me, "listen to the cadence of rest." Then he gives me an example I can understand. "Martin Luther King, the most famous speech of his life. Listen to the cadence: Free at last. (Rest) Free at Last. (Rest) Thank God almighty, we are free at last."