Which opera has more parts including acts and tableaux, Le roi d'Ys or Stiffelio?
Stiffelio Stiffelio is an opera in three acts by Giuseppe Verdi, from an Italian libretto by Francesco Maria Piave. The origin of this was the novel “Le pasteur d’hommes”, by Émile Souvestre, which was published in 1838. This was adapted into the French play "Le pasteur, ou L'évangile et le foyer" by Émile Souvestre and Eugène Bourgeois. That was in turn translated into Italian by Gaetano Vestri as "Stifellius"; this formed the basis of Piave's libretto.
Orlando furioso (Vivaldi, 1714) Orlando furioso RV 819 (] , Teatro San Angelo, Venice 1714) is a three-act opera surviving in manuscript in Antonio Vivaldi's personal library, only partly related to his better known Orlando furioso (RV 728) of 1727. It is a recomposition of an "Orlando furioso" written by Giovanni Alberto Ristori which had been very successfully staged by Vivaldi and his father's "impresa" in 1713, and whose music survives in a few fragments retained in the score of RV 819. Therefore, Vivaldi's first cataloguer Peter Ryom did not assign the opera a RV number, but catalogued it as RV Anh. 84. The libretto was by Grazio Braccioli.