The musical film was a natural development of the stage musical after the emergence of sound film technology. Typically, the biggest difference between film and stage musicals is the use of lavish background scenery and locations that would be impractical in a theater. Musical films characteristically contain elements reminiscent of theater; performers often treat their song and dance numbers as if a live audience were watching. In a sense, the viewer becomes the diegetic audience, as the performer looks directly into the camera and performs to it.