Before revision: The only exceptions were ballad operas, such as John Gay's The Beggar's Opera (1728), musical burlesques, European operettas, and late Victorian era light operas, notably the Savoy operas of W. S. Gilbert and Arthur Sullivan, all of which types of musical entertainments frequently spoofed operatic conventions .
After revision: ; these genres contributed significantly to the emergence of the separate but closely related art of musical theatre in the late 19th centuryThe only exceptions were ballad operas, such as John Gay's The Beggar's Opera (1728), musical burlesques, European operettas, and late Victorian era light operas, notably the Savoy operas of W. S. Gilbert and Arthur Sullivan, all of which types of musical entertainments frequently spoofed operatic conventions .