CHAP. IV.] 



WIND INSTRUMENTS. 



177 



is necessary to stop up the aperture of the bell, in a more or less 

 complete manner with the closed hand ; it is difficult, however, to 

 obtain in this way very just and pure notes. The stopping of the 



Fir;. 128. Cornet a piston. 



aperture in the bell, takes away much of the brilliancy and sonorous- 

 ness of the tones. The musical resources of brass instruments have 

 been increased by modifying in different ways the length of the tube, 



FIG. 129. Section with raised pistons. 



FIG. 130. Section with pistons lowered. 



or of the column of air put into vibration. Holes are pierced at 

 convenient distances, furnished with keys, which open and close the 

 metal sides of the instrument at will. The ophicleide is one of these. 



N 



