FIG. 191.—1, kettledrum; 2, bass drum; 3, cymbals.
FIG. 192.—The seating arrangement of the Philadelphia orchestra.
In the brass wind instruments such as horn, trombone, and trumpet, the lips of the player vibrate and excite the air within. Varying pitches are obtained partly by the varying wind pressure of the musician; if he breathes fast, the pitch rises; if he breathes slowly, the pitch falls. All of these instruments, however, except the trombone possess some valves which, on being pressed, vary the length of the tube and alter the pitch accordingly. In the trombone, valves are replaced by a section which slides in and out and shortens or lengthens the tube.
274. The Percussion Instruments. The percussion instruments, including kettledrums, bass drums, and cymbals, are the least important of all the musical instruments; and are usually of service merely in adding to the excitement and general effect of an orchestra.
In orchestral music the various instruments are grouped somewhat as shown in Figure 192.
CHAPTER XXIX
SPEAKING AND HEARING
