This paper discusses the role of music in different plays such as the classic film, Casablanca. The song "As Time Goes By" was composed by Herman Hupfeld and originally sung by Frances Williams in 1931 on Broadway in a show called Everybody's Welcome. It would go on to play a major part in both the stage play; Everybody Comes to Rick's, as well as the play's film version, Casablanca. Steiner utilizes the song to great effect, both dietetically and non-digetically, in a way that is perhaps unparalleled by any other movie. Dietetically, when performed by Sam the piano player, the song is of great significance to the lead characters. Non-digetically, the song is used in a number of incarnations to emphasize dramatic and emotional moments in the film. In a sense, one could consider "As Time goes By" to be the third lead in the film, alongside the characters of Rick and Ilsa.