The greatest single piece of dance music ever written is The Blue Danube by Johann Strauss. It appears at a critical point in three movies, all favorites of mine. In each case it demonstrates the emotional power of the right music at the right time in the plot. The first movie is an obvious use. Yul Brynner dances with Ingrid Bergman toward the end of Anastasia to this waltz. This occurs at the point where he begins to see that the woman he was grooming to pretend to be the surviving Anastasia, might actually be that surviving member of the...