2Q6 



MUSICAL INSTRUMENTS 



tubes or pipes of different lengths. The air column is thrown 

 into vibration either directly, by blowing across a narrow 

 opening at one end of a pipe as in the case of the whistle, or 

 indirectly, by exciting vibrations in a thin strip of wood or 



metal, called a reed, which in turn 

 communicates its vibrations to the 

 air column within. 



The snorter the air column, the 

 higher the pitch. This agrees with 

 the law of vibrating strings which 

 gives high pitches for short lengths. 

 The pitch of the sound emitted 

 by a column of air vibrating within 

 a pipe varies according to the fol- 

 lowing laws : 



1. The shorter the pipe, the 

 higher the pitch. 



2. The pitch of a note emitted 

 by an open pipe is one octave 

 higher than that of a closed pipe of 

 equal length. 



3. Air columns vibrate in seg- 

 ments just as do strings, and the 

 tone emitted by a pipe of given 

 length is complex, consisting of the 



fundamental and one or more overtones. The greater the 

 number of overtones present, the richer the tone produced. 



273. How the Various Pitches are Produced. With a pipe 

 of given length, for example, the clarinet, (Fig. 189, i) dif- 

 ferent pitches are obtained by blowing hard or gently, thus 

 causing increased 'or decreased vibration of the reed ; also by 

 pressing keys which open holes in the tube and thus shorten 

 or lengthen the vibrating air column, and produce a rise or 



FIG. 188. Open organ pipes of 

 ' different pitch. 



