In the second act, the villains of this opera swear an oath of vengeance in "Der Rache Werk" just before the heroine appears 
In the second act, the villains of this opera swear an oath of vengeance in "Der Rache Werk" just before the heroine appears and sings "Euch L?ften, die mein Klagen" at the beginning of the Balcony Scene.  That heroine's first act soliloquy "Einsam in tr?ben Tagen" describes her dream of the title character, who is forced to leave after Ortrud goads the heroine into asking the title character his name.  A mechanical error during a performance led Leo Slezak to quip, "What time does the next swan leave?"  The Bridal Chorus plays during Elsa's marriage in, FTP, this Wagner opera centering on the titular son of Parsifal.
In the second act, the villains of this opera swear an oath of vengeance in "Der Rache Werk" just before the heroine appears and sings "
Lohengrin