(Fr. acte; Ger. Aufzug; It. atto).
One of the main divisions of a drama, opera or ballet, usually completing a definite part of the action and often having a climax of its own. Although ancient Greek drama was not divided thus except by the periodic intervention of the chorus, and the division into acts of the plays of Roman authors such as Plautus is the work of later hands, Horace (Epistle to the Pisos) recommended five acts as the proper manner of dividing a play. In attempting to recreate the ancient drama this structure was adopted in early operas and was usually preserved in serious French opera of the 17th and 18th centuries even when the three-act form had become established in other types of opera. Rousseau (Dictionnaire de musique, 1768) insisted that the unities of time and place should be observed in each act even in the ‘genre merveilleux’. But there were already many exceptions (e.g. Rameau’s Hippolyte et Aricie, 1733, in which the fifth act embraces two tableaux), and the development of stage techniques that afforded ways of presenting transformation scenes, together with the relaxation of the unities and the more fluid requirements in the representation of time and place in Romantic opera, meant that Rousseau’s principles were soon discarded. From the late 18th century, operas were written in anything from one to five acts and, particularly in works for the popular theatre, little attempt was made to observe the unities of time and place (e.g. Mozart’s Die Zauberflöte has two acts and a total of 13 scenes, most of which have different settings). Wagner’s ideal music drama was to consist of three acts. He regularly adopted this division in his mature works, but other composers and librettists have remained unconvinced of the need for so restrictive a practice.
Most oratorios are divided into parts rather than acts, but Handel, whose works in this genre were conceived in theatrical terms, used the latter expression. It was also employed in England during the 18th and early 19th centuries for the various subdivisions of a concert.
MICHAEL TILMOUTH