James Hamilton Haskell, second-generation owner of a struggling music store, is invited to go into business with his uncle, Charles J. Haskell, a wealthy health food magnate and sponsor of a weekly radio program, "Haskell's Happiness Hour." Unfortunately for C. J., who detests music, his factory is across the alley from the strong-willed Mom McCorkle's boardinghouse, which is currently home to Horace Heidt and his band. When debts force Jimmy to close his music store, he decides to take his uncle up on his offer, but along the way he meets Mom's pretty daughter Molly, a singer with Horace's band. While Molly is describing her family's longstanding feud with C. J., his employee, Jasper, shows up with the police and demands that the music stop. Jimmy lobs a tomato at Jasper, but it hits C. J. instead, and a delighted Mom rewards him with a free room. Later, Lt. Grady shows up and, after Molly credits Jimmy with the tomato attack, reluctantly arrests him. Judge Murray has just postponed the trial and released Jimmy on bail when C. J. barges into the courtroom, and Jimmy, afraid of being identified as a Haskell, sneaks out and ends up locked in a paddy wagon. The judge cites C. J. for contempt and sends him to jail, where he finds Jimmy entertaining the other prisoners with his harmonica. Upon his release, Jimmy learns that the band members pawned their instruments to post his bail. When C. J. gets out of jail that night, he is too hoarse to do his radio program, having been forced to participate in singalongs with his cellmates, so Jimmy fills in for him and is heard by Horace and Willie, Molly's brother. Later that night, Jimmy sneaks out of C. J.'s mansion and returns to the boardinghouse, where he is confronted by Willie and Horace. After Jimmy confesses that C. J. is his uncle and pays to get the band's instruments out of hock, Willie and Horace decide to help him by getting C. J. out of the way. Posing as a professor, Horace accompanies Jimmy to C. J.'s home, while the band hides in the furnace room and plays loudly. When Jimmy and the "professor" claim not to hear the music, C. J. decides to take a trip to Canada to rest his nerves. The next day, Jimmy calls on broadcasting executive J. K. Louderman and, after wresting control of the program from Jasper, arranges for Horace's band to perform on the next show. The broadcast is a big success, but the happy mood is broken when Jasper reveals Jimmy's identity to Molly. Feeling betrayed, Molly goes to the microphone and announces that, beginning with next week's broadcast, $1,000 will be given away during every show. C. J., who has been listening to the broadcast at a Canadian trading post, is apoplectic, and begins the long journey home. The next day, C. J.'s lawyer asks Jimmy to sign a statement declaring Molly responsible for the giveaway idea, knowing that a judgment against the McCorkles would enable C. J. to take their property, but Jimmy refuses. Louderman then arrives with Samson, a government official, who warns Jimmy that while he is legally obligated to give the money away, he may not use lotteries, raffles or contests to do so. Jimmy wracks his brain to figure out how to give the money away, and finally, on the night of the broadcast, the sound of the chiming clock gives him an idea. Using phone books from all over the country, Jimmy and Molly spin a carnival wheel to select the winner, Olaf Svenson of Minnesota. C. J. arrives as the broadcast is underway, and is about to call a halt to the proceedings when Louderman introduces him to two advertising men eager to buy the show. C. J. and Mom McCorkle bury the hatchet, and Jimmy announces over the air that he and Molly will soon be married.