THE KINDS OF STRINGED INSTRUMENTS 293 



The vibrations of the fork are transmitted to the table top 

 and throw it into vibrations similar to its own, and these addi- 

 tional vibrations intensify the original sound. Any fork, no 

 matter what its frequency, can force the surface of the table 

 into vibration, and hence the sound of any fork will be intensified 

 by contact with a table or box. 



This is equally true of strings; if stretched between two 

 posts and bowed, the sound given out by a string is feeble, 

 but if stretched over a sounding board, as in the piano, or 

 over a wooden shell, as in the violin, the sound is intensified. 

 Any note of the instrument will force the sounding body to 

 vibrate, thus reenforcing the volume of sound, but some tones, 

 or modes of vibration, do this more easily than others, and 

 while the sounding board or shell always responds, it re- 

 sponds in varying degree. Here again we have not only en- 

 richment of sound but also individuality of instruments. 



271. The Kinds of Stringed Instruments. Stringed instru- 

 ments may be grouped in the following three classes : 



a. Instruments in which the strings are set into motion by 



hammers piano. 



b. Instruments in which the strings are set into motion 



by bowing violin, viola, violoncello, double bass. 



c. Instruments in which the strings are set into motion by 



plucking harp, guitar, mandolin. 



a. The piano is too well known to need comment. In 

 passing, it may be mentioned that in the construc- 

 tion of the modern concert piano approximately 

 40,000 separate pieces of material are used. The 

 large number of pieces is due, partly, to the fact 

 that the single string corresponding to any one key 

 is usually replaced by no. less than three or four 

 similar strings in order that greater volume of 

 sound may be obtained. The hammer connected 



