Which opera  Pelléas et Mélisande and Die schweigsame Frau has fewer acts ?
Pelléas et Mélisande (opera) Pelléas et Mélisande ("Pelléas and Mélisande") is an opera in five acts with music by Claude Debussy. The French libretto was adapted from Maurice Maeterlinck's Symbolist play "Pelléas et Mélisande". It premiered at the Opéra-Comique in Paris on 30 April 1902 with Jean Périer as Pelléas and Mary Garden as Mélisande in a performance conducted by André Messager, who was instrumental in getting the Opéra-Comique to stage the work. The only opera Debussy ever completed, it is considered a landmark in 20th-century music.
Bluebeard (ballet) Barbe-bleue (en. "Bluebeard") (ru. «Синяя борода», "Sinjaja boroda") is a "ballet-féerie" in three acts and seven scenes, originally choreographed by Marius Petipa to the music of Pyotr Schenk. The libretto was created by the author and dramatist Countess Lydia Pashkova from the fairy tale "Bluebeard" by Charles Perrault. The ballet was first presented by the Imperial Ballet on December 20 [O.S. December 8] 1896 at the Imperial Mariinsky Theatre in St. Petersburg, Russia, the first performance being a benefit in honor of Marius Petipa's fiftieth anniversary in service to the St. Petersburg Imperial Theatres.