=Bach and Handel=.—We now come to the period of Bach and Handel, each distinct in methods, the latter the more immediately influential in the development of the orchestra, the former’s principles of writing in the =polyphonic style= not being taken up until after years by Wagner and more recently by the extreme modern composers with their free polyphony. In a Bach score each instrument had an independent part to sing, and was treated from a musical standpoint, whereas the tendency of other composers was to seek figures and passages which should be characteristic of the instrument, the standpoint of effect. This particularly applies to the wind instruments. =Handel’s= idea seemed to be the building up of great =mass effects=, his style partook of the =harmonic= rather than the polyphonic. He used all the important instruments found in the modern orchestra except the _clarinet_, although the proportion of the wind instruments to the strings is greater, due to the relatively inferior power of these instruments in Handel’s time. =Haydn and Mozart=.—From Handel we pass to the first of his three great successors, =Haydn=, who has been called the “father of the symphony,” who determined, in fact, the course of orchestral development. And we should not overlook the fact before-mentioned, namely, that the professional violinists, most of whom were also directors of orchestras in the pay of great princes, were testing the capacities and resources of the instruments used. In the period which Haydn represents, the _proportions of the instruments_ in the orchestra were definitely _fixed_ and the size of the string band became relatively greater, the _’cello_ coming in to greater prominence in its use as a _melody instrument_. Haydn’s last symphony, written in 1795, calls for two flutes, two oboes, two clarinets, two bassoons, two kettle drums, and the usual string band. This was the combination which Haydn selected as the most useful and effective, as the result of his experience as a conductor for many years. It was to =Mozart= that the introduction of the =clarinet= into the orchestra is due, for Haydn did not employ this instrument in his earlier works. The clarinet began to take an effective form about the end of the 17th century, yet it was not until the 19th century that it received the improvements that now make it one of the most useful instruments in the orchestra, with a wonderfully facile technic and correct intonation. The greatest of these changes was the application, to the clarinet, of the system of keys and fingering invented by =Theobald Boehm= (1794-1881) for the flute. In addition to showing the value of the clarinet as an instrument, Mozart pointed the way to some uses of the =trombone=. His E-flat Symphony is scored for one flute, two clarinets, two bassoons, two horns, two trumpets, tympani and strings; in the score of the “Jupiter” symphony, the clarinet does not appear.