Musicals focus on stories in which characters communicate their feelings through music and dance. Rather than simply providing a lapse in a movie's action, song and dance fuse to form a whole -- and here lies the main difference between a musical and a movie just containing occasional musical numbers. Because of the difficulty in explaining away as stagey a technique as the song which leaps out of a narrative, as films in general pushed towards realism in the '60s and '70s, the musical fell out of favor. While there have been occasional attempts to recapture the magic -- Pirates of Penzance, Evita -- there have been very few unqualified successes on the level of My Fair Lady, Sound of Music, or West Side Story. The hey-day of the musical began with the very advent of sound film, as the Jazz Singer was one of the first talkies. Stars such as Gene Kelly, Fred Astaire and Bing Crosby had film careers which would have been all but impossible in the latter decades of the 20th century, so tied up in the musical were they. Much of the glamour and magic of the cinema was related to these stars and their songs, and they continue to be well-loved despite the lack of successful contemporary musicals.