Bagatelle is a one-act opéra-comique by Jacques Offenbach, with a French libretto by Hector Crémieux and Ernest Blum.
Her maid Finette is having an affair with a clarinetist reduced to playing in the Cirque Fernando band, Pistache.
After a performance, Bagatelle is rehearsing a peasant song when an 18-year-old young admirer enters through the window.
He is Georges de Planteville and to ensure they stay together he throws the keys through the window.
It emerges that Georges had defended Bagatelle during her show against detractors, so she returns his love.