While the subject of this book, movie musicals, is one of the most popular genres of film, it is difficult to describe exactly what constitutes a musical. Most films have soundtracks. And many include a few musical numbers, but how much musical content does a film need before it is officially a musical? Since there are no clear-cut rules, I based this book on a few simple guidelines. First, I excluded all silent films, for obvious reasons. Second, I excluded movies where the musical numbers were not performed by the stars of the film, or movies that are basically comedies or dramas, but include a little music. Third, I excluded concert films or any films that did not have a plot. Finally, since this is a book of images, I tried to always give preference to posters that depict people singing or dancing. It is clear that early movies were dominated by a relatively small group of wonderful performers such as Alice Faye, Betty Grable, and, of course, Fred Astaire and Ginger Rogers.