Marvin Howe is a hired hand at the Clover Leaf Dairy Farm in Rutledge, Vermont, who, much to the consternation of the dairy's owner, "Pop" Turnbull, spends most of his time practicing the trombone, not doing his chores. After Marvin and Pop's daughter Juanita announce their engagement, Tate Winters, Marvin's rival for Juanita's affections, convinces Pop to send Marvin to New York City to get Pop's dairy a membership in the National Dairymen's Association, knowing that Pop has been refused one repeatedly, as he raises goats, not cows. In New York, Jeremiah K. Barton, president of the Dairymen's Association, orders his secretary, Lucille Rose, to give Marvin "the brush off," but when she tells the farm boy that Barton will be in conference for a week, Marvin takes a room at a boardinghouse owned by a Mrs. Forbes. The landlady's son Skinnay offers Marvin a membership in his jazz band after hearing him play his trombone. Skinnay's friend Dolly O'Brien then convinces Marvin to take a job with the band at O'Brien's Rendevous, a nightclub owned by her uncle, Big Mike O'Brien. Marvin becomes a national sensation known as "The Hot Toot" when he knocks out "zoot suiter" gang leader Alphonse, who attempts to destroy the nightclub after being fired by Big Mike. Pop then takes Juanita to New York to show her how "the big city" has changed Marvin, and when she is misled to believe that Dolly is Marvin's new girl friend, Juanita breaks their engagement and goes back to Rutledge. At the same time, Barton and his associate, Peterson, offer Big Mike a national radio contract for Skinnay's band. Marvin is so heartbroken, however, that he quits the band and returns to Rutledge as Juanita and Tate are about to be married. The band follows him there, and Dolly tells all to the bride-to-be. Marvin and Juanita are reunited just in time for the band to perform on its first coast-to-coast radio broadcast.