Which opera  Pelléas et Mélisande and Die schweigsame Frau has fewer acts ?
Die schweigsame Frau Die schweigsame Frau ("The Silent Woman"), Op. 80, is a 1935 opera in three acts by Richard Strauss with libretto by Stefan Zweig after Ben Jonson's "Epicoene, or the Silent Woman".
L'Olimpiade (Pergolesi) L'Olimpiade is an opera in the form of a dramma per musica in three acts by the Italian composer Giovanni Battista Pergolesi. Pergolesi took the text, with a few modifications, from the libretto of the same name by Pietro Metastasio. The opera first appeared during the Carnival season of 1735 at the in Rome and "came to be probably the most admired" of the more than 50 musical settings of Metastasio’s drama.