Musicals focus on stories in which characters communicate their feelings through music and dance. The hey-day of the musical began with the very advent of sound film, as the Jazz Singer, a musical starring Al Jolson, was one of the first talkies. The popularity of the musical made major stars out of performers like Gene Kelly, Bing Crosby, and Fred Astaire, whose chief skills revolved around singing and dance. Animated films often take the narrative form of musicals, from Snow White and the Seven Dwarves -- the first full length animated feature - to later animated movies like Fantasia and Beauty and the Beast. The musical's prevalence peaked in the '50s and 60's, with films like My Fair Lady, Sound of Music, and West Side Story, but the genre subsequently declined in favor. Characters in a musical will go from speaking their dialogue one moment to singing it the next, with no acknowledgement of the change; this fantastical element proved harder and harder for audiences to accept, as films in general pushed towards realism in the '60s and '70s. There have been attempts to recapture the magic of the musical's golden era every few years, sometimes resulting in a minor resurgence in popularity for the genre, as was the case with Pirates of Penzance, Fame, Evita, Moulin Rouge!, and Mamma Mia!, to name a few. However, few musicals have achieved the success of works made during the pre-'60s period.