Baby Beats the Band is a French film. The French version directed by Jean Boyer and there is also an English version, Monte Carlo Baby, co-directed by Jean Boyer and Lester Fuller. The film was released in 1951.
Marinette, the flighty daughter of a nanny in Le Vésinet, where a shady impresario has hidden the baby of an American star, has mistaken it for Nicolas, the grandson of Max Elloy, drummer of the Ventura Orchestra. She makes him give it to her as Elloy is about to take the train to the Monte Carlo Jazz Festival where the orchestra will perform. But Elloy was afraid that if he took the boy, Ventura would replace him with another drummer. So he imagines placing the child in Ventura’s compartment and passing him off as the biological son of one of the musicians in the orchestra, abandoned by his mother. Meanwhile, in Le Vésinet, the nanny returns from the provinces, finds that her daughter has the wrong child, and sends her to Monaco to get him back by any means necessary. The child’s father also tries to get the child back. A vaudevillian situation ensues, with many misunderstandings. All’s well that ends well though.