Verdi's musical focus was almost without exception on opera—he wrote over two dozen in all, and many are central repertoire works. His Requiem is the only non-stage work to be performed regularly, and there are occasional outings for his lovely String Quartet. In opera, though, he refined and extended the form's power and expression, giving us such masterpieces as La traviata, Il trovatore, Don Carlos, Aida and Otello. His last opera, Falstaff (1893), written when he was 80, is a magnificent culmination of his art inspired by his beloved Shakespeare. Along with Wagner, Verdi raised opera to a new level.