Film scholar David Bordwell refers to the years 1917–1960 as the classical era of filmmaking in Hollywood. Bordwell defines the era's style as being governed by straightforward narrative considerations, i.e., the need to follow well-defined characters through a chronological sequence of events, or plot. The technical elements of filmmaking—camera movement, lighting, editing, and sound—are all employed to tell a realistic story, one in which the world of the story is self-sufficient and recognizably related to our own. Devices that draw attention to the film as film rather than to the story are avoided.

Within this definition, the musical films of the 1930s are anomalous in that they interrupt narrative to present musical performances only tangentially related to the plot. In one film directed by Busby Berkeley, for example, a scene begins with a shot of an audience watching a singer. The singer's face then fills the screen—a natural enough transition—but this image soon dissolves into a fanciful sequence consisting of various aerial views of city life. Although the sequence illustrates the song being sung, it does not contribute to the story Berkeley tells between musical numbers. In such sequences, filmmaking techniques are used not to advance a narrative but as a respite from narrative; the people we see are not characters in a plot but rather are abstracted figures; editing and camera movement function not to help tell a story but to manipulate images into intricate patterns. Can the musical—in which such differently motivated and constructed sequences abut so closely—fit comfortably within Bordwell's definition of the classical style?

Bordwell's response is that the musical, no less than comedy or melodrama (two other staples of the classical era), evolved from popular live theater. The musical's conventions, Bordwell argues, cue viewers to expect a different structure—alternating narrative scenes and self-contained performances—from that of other genres, a structure that audiences are prepared for and thus accept as "realistic." But raising the issue of genre does not disguise the fact that Bordwell stretches the definition of the term "realism," for there is still the problem exemplified in films such as Berkeley's by the fact that the musical performances are not merely self-contained but self-absorbed—the selfish aesthetic of the interlude isn't intended to advance the plot but instead to draw attention to its own artistic expertise. Even the viewer aware of the film's genre cannot remain entirely unfazed by the break in the film's "reality." Bordwell too quickly dismisses the fact that watching a film is a perceptual act and not an academic exercise in pigeonholing genres. Because knowledge of genre is acquired, it would be worthwhile for scholars like Bordwell to first consider how viewers process cinematic images and eventually come to accept them as conventions before generalizing about the realism of certain film styles.