WIND INSTRUMENTS 



287 



FIG. 149. i, clarinet ; 2, oboe ; 3, dute. 



The shorter the air column, the higher the pitch. With a 

 pipe of fixed length, for example, the clarinet (Fig. 149, i), 

 different pitches are obtained by pressing keys which open 

 holes in the tube and thus shorten or lengthen the vibrating 

 air column and produce a rise or fall in pitch. Changes in pitch 

 are also produced by variation in the player's breathing. By 

 blowing hard or gently, 

 the number of vibra- 

 tions of the reed is in- 

 creased or decreased and 

 the pitch is altered. 



Intheoboe (Fig. 149,2) 

 the vibrating air column 

 is set into motion by 

 means of two thin pieces 

 of wood or metal placed in the mouthpiece of the tube. Vari- 

 ations in pitch are produced, as in the clarinet, by means of 

 stops and varied breathing. In the flute, the air is set into 

 motion by direct blowing from the mouth, as is done, for in- 

 stance, when we blow into a 

 bottle or key. 



The sound given out by 

 organ pipes is due to air 

 which is set into vibration 

 as it is blown across a sharp 

 edge at the opening of a 

 narrow tube. This vibra- 

 tion is communicated to the 

 air within the organ pipe. 

 In order to obtain the differ- 

 ent pitches, pipes of different 

 lengths are used. The mechanism of the organ is such that 

 pressing a key allows the air to rush into the communicating 



I 2 



FIG. 150. i, horn ; 2, trumpet ; 

 3, trombone. 



