CHAP, iv.] WIND INSTRUMENTS. 173 



by the periodical vibrations of the air. The number of vibrations, 

 it is true, determines the pitch of the note. It is necessary, then, 

 that the reeds adapted to a pipe be of proper dimensions and formed 

 of a substance with a certain elasticity in order that its vibrations be 

 isochronous with those of the column of air of the pipe. The curved 

 wire also enables this result to be obtained. We shall see, when 

 speaking of organ stops, how the notes produced are modified by the 

 reeds, by adapting them to pipes of various forms which then are 

 called cornets d'harmonie. 



A word now on musical instruments sounded by means of reeds 

 differing slightly from those adapted to organ pipes, but otherwise, 

 vibrating in the same manner. First comes the clarionet, with the 

 mouthpiece formed by a reed fitted to a pipe of box-wood, ebony 

 or ivory, which the performer causes to vibrate by blowing into the 

 narrow aperture which separates them. The performer's lips by 

 pressing with more or less force against the two sides of the mouth- 

 piece of the instrument, act as the curved wire and regulate the 

 pitch of vibrations. 



As in the flute, the intermediate notes of the diatonic and chro- 

 matic scales are obtained, by uncovering the holes successively or 

 simultaneously, either by raising the fingers, or pressing on the keys 

 or valves of the instrument. The pipe or body of the clarionet is 

 terminated by a sort of bell, shown in Fig. 120. 



The reed of the hautboy is formed of two thin layers of reed 

 slightly carved in their cross sections, and placed one against the 

 other, their edges and concavities facing each other ; in the per- 

 former's mouth, they vibrate under the influence of the current of air 

 produced by the breath, and the length of the vibrating part depends 

 on the way in which the elastic plates are pressed by the lips. 



The bassoon is the same kind of instrument as the hautboy but 

 formed of pipes of much greater volume and producing notes two 

 octaves lower in pitch than the havitboy. The bassoon therefore is to 

 the hautboy what the violoncello is to the violin. 



