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.
Sly (opera) Sly, ovvero La leggenda del dormiente risvegliato (English: "Sly, or The Legend of the Sleeper Awoken") is an opera in three acts by Ermanno Wolf-Ferrari to an Italian libretto by Giovacchino Forzano, based on the Induction (the Prologue) to William Shakespeare's "The Taming of the Shrew" (the German version of libretto, "Sly, oder Die Legende vom wiedererweckten Schläfer", was translated by ). Unlike most of Wolf-Ferrari's other operas, this is a tragedy.