=Influence of the Opera=.—The first composers of opera and oratorio gave instrumental support to the singers, although it was very meager. Yet the opera gave the help of that great principle of invention, necessity, and composers began to experiment with various combinations of instruments to secure a more adequate accompaniment for the voice as well as to heighten the effects demanded by the drama. =Monteverde=, an independent thinker and innovator, marked out lines in which efforts should be made by successors. He studied the _characteristic effects of_ the various _groups_ and made use of them as he felt them. His orchestra for “Orfeo” (1608) was made up of two harpsichords, ten tenor viols, two bass viols, two “little French violins,” one double harp, two organs of wood, one regal, two viole de gamba, two large guitars, two cornets, two trombones, three trumpets with mutes, one octave flute, one clarion. The most significant item is found in the “little French violins,” which presages the appearance of the instrument which was, a century later, to be recognized as the backbone of the orchestra. Among the distinctive instrumental effects which Monteverde introduced was the =tremolo= for bowed string instruments as well as the =pizzicato=. In looking over the instruments of Monteverde’s orchestra we will note but _one_ wood wind, the flute. This shows that composers, doubtless through the military use of brass and drums, had accepted the latter as means for special effects. Instruments of the _wood wind_ type were still too _crude_ to be admitted. =Alessandro Scarlatti=, who did so much for the opera from the side of form and content, also contributed to the development of orchestral music. He evidently perceived the importance of having a nucleus around which to build his harmonies, a group of instruments which should furnish a firm support and which could blend the various tone qualities. With the intuition of genius he selected the =string tone= for this purpose, and in this he was greatly aided by the fact that the Amati family, and their successors, Guarnerius and Stradivarius, had already perfected the violin, although the great players were yet to come. Scarlatti wrote in four parts for the string instruments, the treble part to the first violin, the alto to the second, the tenor part to the viola, which previously had often played in unison with the double bass, while the bass part was taken by ’cellos and basses. He also added =oboes= and =bassoons= to the strings and brass. Lully in France used an orchestra similar to that adopted by Scarlatti. The =kettle-drums= now come into use. The works of Corelli and his violinist successors, which showed the possibility of writing for strings, undoubtedly influenced orchestral writing.