When a romantic orchestra won't change their boring style into something more modern to get gigs, their girlfriends split and form a rock and roll orchestra that quickly becomes talk of the town. The guys are furious since they are relegated to their opening act as a comical number, but when the League of Virtue protests against the new satanic music, the old-fashioned music seems to win the day.

A frustrated big-band promoter runs in to rock-and-rollers Bill Haley and the Comets at a small-town dance. He quickly becomes their manager and, with the help of Alan Freed, hopes to bring the new sound to the entire country. But will a conniving booking agent, with a personal ax to grind with the manager, conspire to keep the band from making the big time?

Six-year-old "Mike" goes to live with her pregnant older sister, Babs, who plays string bass in José Iturbi's orchestra. And the orchestra is rapidly turning completely female, what with the draft. As the orchestra travels around the country, Babs' fellow orchestra members intercept and hide her War Office telegram to protect the baby.