Le Roi du swing

After their annual free concert at Chicago's Dearborn Settlement, Benny Goodman and his band are packing up to move on to their next engagement at a military camp, when a kid, Tony Birch, steals Goodman's clarinet. Goodman and Popsie pursue him to a tenement flat where he has led them to hear his brother, Johnny Birch, play the trombone. Goodman offers him a job, over Popsie's protest, with the band.