(Ger. Nummernopera; It. opera a numeri).
Term for an opera consisting of individual sections or ‘numbers’ which can readily be detached from the whole, as distinct from an opera consisting of continuous music. The term is best applied to the various forms of 18th-century opera, including opera seria, opera buffa, opéra comique, ballad opera and Singspiel as well as to some 19th-century grand operas. Under the influence of Wagner’s ideas about the relationship between opera and drama, the number opera became unfashionable, and neither his operas nor those of late Verdi, Puccini and the verismo school can be so called, although arias can easily be detached (at the point designed to accommodate the applause). In spite of the widespread adherence to Wagner’s aesthetic of continuous music drama, some notable 20th-century works can be considered number operas, such as Berg’s Wozzeck (1925) and Stravinsky’s deliberately archaic The Rake’s Progress (1951).
For bibliography see Opera, §VII.