The story unfolds in late 1930s America’s Deep South, inevitably bringing up unpleasant racial issues. The film seems to try and imply that despite this, perhaps some early signs of integration were beginning, utilizing jazz music and the familiar appeal of Bing Crosby as symbols. A young man nicknamed “Jeff” demonstrates remarkable musical ability but is often scolded by his father for performing with bands comprised of Black musicians in New Orleans. He matures—becoming Bing Crosby—and forms a band that includes people of different races and talents. The group encounters prejudice within the city, and their fortunes begin to change when they meet singer “Betty Lou” (Mary Martin). A fairly standard romantic rivalry develops as he finds himself attracted to her, but so does his close friend, the cornet player "Memphis" (Brian Donlevy). This love triangle essentially serves as the film's narrative framework—a familiar trope. The movie’s primary focus is on the numerous musical performances that are likely to get your foot tapping and possibly inspire a 1941 audience to appreciate talented performers regardless of their race, creating an impressive sound (aside from Donlevy’s apparent lack of instrumental skill). While the songs themselves feel somewhat disposable and might not linger in memory, they effectively serve their purpose as the United States prepares for a difficult period ahead, allowing Bing Crosby to showcase why he was such a popular entertainer.

Source on TMDB