Which opera features the humming chorus?

The humming chorus is featured in Giacomo Puccini's Opera "Madama Butterfly." This piece occurs in Act II, where the chorus hums softly, creating a serene atmosphere as Cio-Cio-San awaits the return of her husband, Pinkerton. The haunting quality of the humming enhances the emotional depth of the scene, reflecting themes of longing and hope.