Singin' in the Rain, The Sound of Music, Camelot--love them or love to hate them, movie musicals have been a major part of all our lives. They're so glitzy and catchy that it seems impossible that they could have ever gone any other way. But the ease in which they unfold on the screen is deceptive. Dorothy's dream of finding a land "Somewhere Over the Rainbow" was nearly cut, and even a film as great as The Band Wagon was, at the time, a major flop.

In Dangerous Rhythm: Why Movie Musicals Matter, award winning historian Richard Barrios explores movie musicals...