orchestra in its earliest form; both the use and the effect of various instruments are very imperfectly known, and the instrumentation is consequently more or less incomprehensible. But here too development proceeded in the way of simplification, and at the time of Scarlatti the treatment of instrumental accompaniment and the disposal of the orchestra was determined as to essentials for all future times. In the plain recitative of the dialogue, the fundamental note was given by the bass, and the chord was struck on the piano (at which the composer or kapellmeister conducted) and repeated as often as necessary. In the songs and _ensembles_ the instruments came in as accompaniments, freed from the obligation of following a given melody step by step with a given bass, according to the rules of thoroughbass for filling up harmonies. Scarlatti and the earlier masters kept this accompaniment very simple, seldom introducing more than one part in addition to the bass and the voice. But, as practised contrapuntists, they could handle the accompanying parts broadly and freely, and could give animation by simple means. This art gradually decreased, and the accompaniment, although fuller, became more mechanical and dependent, Only here and there suggesting contrapuntal elaboration. The orchestra was used independently only in the symphonies which repeated the motifs of the songs, in the short interludes of accompanied recitative, and finally in the introductory overture or sinfonia. Italian operatic composers began by making use of the form of overture which Lully had established in France, beginning with an adagio, followed by a quick movement, often in the form of a fugue, and passing again into an adagio, which concludes the overture. Later, the form was determined which has remained ever since, of three movements: an allegro, a slower, shorter movement contrasting in time, instrumentation, and expression, and a concluding allegro, animated and often noisy. These main features were capable of rich and varied development, were it not that in Italy little importance was attached to the overture, which was commonly regarded as a {OPERA SERIA.} (166) means of reducing the audience to silence and attention. The three movements, therefore, generally preserved their gradations without marked characteristics, and the attempt to express the effect of the first scene by means of the overture was soon abandoned.[24]