Éraste, Madame Amelin's nephew, is about to marry Angélique. To thank his aunt for her consent, the young man asks his valet, Merlin, to orchestrate an entertaining comedy. In the midst of the rehearsal, the real feelings of the actors and the servants soon mingle with the comedy.
Antoine is a violinist in love with sweet Sophie. Problem: his sweetheart is the daughter of the master of the municipal harmony, a stubborn man who swears only by the brass. Never mind: Antoine decides to ask him for his daughter's hand and to win his place at the orpheon. Will the two men be able to get in tune?