The musical film is a film genre in which songs sung by the characters are interwoven into the narrative, sometimes accompanied by dancing.
The songs usually advance the plot or develop the film's characters, though in some cases they serve merely as breaks in the storyline, often as elaborate "production numbers".
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 there is a live audience watching. In a sense, the viewer becomes the diegetic audience, as the performer looks directly into the camera and performs to it.
The 1930s through the early 1950s are considered to be the golden age of the musical film, when the genre's popularity was at its highest in the Western world.
Musical short films were made by Lee de Forest in 1923–24. Beginning in 1926, thousands of Vitaphone shorts were made, many featuring bands, vocalists, and dancers. The earliest feature-length films with synchronized sound had only a soundtrack of music and occasional sound effects that played while the actors portrayed their characters just as they did in silent films: without audible dialogue.The Jazz Singer, released in 1927 by Warner Brothers, was the first to include an audio track including non-diegetic music and diegetic music, but it had only a short sequence of spoken dialogue. This feature-length film was also a musical, featuring Al Jolson singing "Dirty Hands, Dirty Face", "Toot, Toot, Tootsie", "Blue Skies", and "My Mammy". Historian Scott Eyman wrote, "As the film ended and applause grew with the houselights, Sam Goldwyn's wife Frances looked around at the celebrities in the crowd. She saw 'terror in all their faces', she said, as if they knew that 'the game they had been playing for years was finally over'." Still, only isolated sequences featured "live" sound; most of the film had only a synchronous musical score. In 1928, Warner Brothers followed this up with another Jolson part-talkie, The Singing Fool, which was a blockbuster hit. Theaters scrambled to install the new sound equipment and to hire Broadway composers to write musicals for the screen. The first all-talking feature, Lights of New York, included a musical sequence in a night club. The enthusiasm of audiences was so great that in less than a year all the major studios were making sound pictures exclusively. The Broadway Melody (1929) had a show-biz plot about two sisters competing for a charming song-and-dance man. Advertised by MGM as the first "All-Talking, All-Singing, All-Dancing" feature film, it was a hit and won the Academy Award for Best Picture for 1929. There was a rush by the studios to hire talent from the stage to star in lavishly filmed versions of Broadway hits. The Love Parade (Paramount 1929) starred Maurice Chevalier and newcomer Jeanette MacDonald, written by Broadway veteran Guy Bolton.