HARMONY IN MUSIC. 



77 



of several forms of string marked by the corresponding 

 capital letters in Fig. 4. It is easily seen how greatly 

 this form of wave (which of course could not occur in 



FIG. 5. 



a c e g e 



V* 



water) differs from that of Fig. 3 (independently of mag- 

 nitude), as the string only imparts to the air a series of 

 short impulses, alternately directed to opposite sides. 1 



The waves of air produced by the tone of a violin 

 would, on the same principle, be represented by Fig. 6. 



FIG. 6. 



: 



During each period of vibration the pressure increases 

 uniformly, and at the end falls back suddenly to its 

 minimum. 



It is to such differences in the forms of the waves of 

 sound that the variety of quality in musical tones is due. 

 We may even carry the analogy further. The more uni- 

 formly rounded the form of wave, the softer and milder is 

 the quality of tone. The more jerking and angular the 

 ave-form, the more piercing the quality. Tuning-forks, 

 ith their rounded forms of wave (Fig. 3), have an extra- 

 ordinarily soft quality; and the qualities of tone generated 

 by the zither and violin resemble in harshness the angu- 

 larity of their wave-forms. (Figs. 5 and 6.) 



1 It is here assumed that the sounding-board and air in contact with it 

 immediately obey the impulse given by the end of the string without 

 exercising a perceptible reaction on the motion of the string. 





