The scene is Venice. Hoffmann thinks he's fallen in love with the courtesan, Giuletta. But before the act can get going, Hoffmann's muse, Niklause sings the Barcarolle with Giuletta.
Translation: Beautiful night, oh, night of love, smile on our drunken rapture; night sweeter than day, oh beautiful night of love. Time flies and carries away our tenderness, far from this happy stay, time flies without return. Zephyrs, embrace us with your caresses; give us your kisses.