286 DYNAMICAL THE OK Y OF SOUND 



analysis of compound notes by resonance. If the string c', for 

 example, be freed from its damper by holding down its key, 

 whilst c is sounded for a moment, the harmonic c is taken up 

 and continued by the first-mentioned string. If on the other 

 hand, the string c be free from its damper, whilst c is sounded 

 for a moment, the tone c' is taken up as a harmonic of the 

 lower string. These simple experiments, which (with others) 

 are recommended by Helmholtz, can of course be varied in 

 many ways. Again, when the ear has learnt to distinguish the 

 partial tones in a complex note, it is easy to note the absence 

 of a particular tone of the series when the corresponding simple- 

 harmonic vibration is not excited. For instance, when a string 

 is struck at its middle point, the harmonics of even order are 

 wanting ( 26). 



92. Influence of Overtones on Quality. 



The quality of a musical note is determined ( 2) by the 

 number and relative intensities of the various tones which 

 compose it. The kind of influence which overtones of different 

 ranks exercise on the quality is summarised by Helmholtz, 

 somewhat as follows: 



1. Pure tones like those of tuning forks with resonance 

 boxes, or of wide stopped organ pipes, are soft and pleasing, 

 smooth, but wanting in power. 



2. Notes which contain a series of overtones up to the 

 fifth or sixth in rank are richer and more musical, and are 

 perfectly smooth so long as no higher overtones are sensible. 

 The notes of the piano and of open organ pipes are examples, 

 whilst those of the flute, and of the flute-stops on the organ 

 when softly played, approximate more to the character of pure 

 tones. In the "mixture" stops of the organ the lower 

 harmonics are expressly provided in greater intensity by 

 auxiliary pipes which are played automatically along with that 

 which gives its name to the note. 



3. When the harmonics of even order are absent, as in the 

 case of a stopped organ pipe, or a piano string struck at the 

 middle point, the note has a hollow, and even a nasal character, 

 if the odd harmonics are numerous. 



