He sang a wide variety of roles including parts in operas by Claudio Monteverdi , Mozart , Ravel , Stravinsky , JanÃ Ä ek , Schoenberg and , especially , Benjamin Britten . His repertoire was broad , ranging from the operas of Claudio Monteverdi and Mozart to more modern works by Ravel , Stravinsky , JanÃ Ä ek and Schoenberg .