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.
Musical short films were made by Lee de
Warner Brothers produced the first screen operetta, The Desert Song in 1929. They spared no expense and photographed a large percentage of the film in Technicolor. This was followed by the first all-color, all-talking musical feature which was entitled On with the Show (1929). The most popular film of 1929 was the second all-color, all-talking feature which was entitled Gold Diggers of Broadway (1929). This film broke all box office records and remained the highest grossing film ever produced until 1939. Suddenly the market became flooded with musicals, revues and operettas. The following all-color musicals were produced in 1929 and 1930 alone: The Show of Shows (1929), Sally (1929), The Vagabond King (1930), Follow Thru (1930), Bright Lights (1930), Golden Dawn (1930), Hold Everything (1930), The Rogue Song (1930), Song of the Flame (1930), Song of the West (1930), Sweet Kitty Bellairs (1930), Under a Texas Moon (1930), Bride of the Regiment (1930), Whoopee! (1930), King of Jazz (1930), Viennese Nights (1930), Kiss Me Again (1930). In addition, there were scores of musical features released with color sequences.