1172 



THE EAR. 



the tones of the reed. These experiments show — (1) That many sounds 

 which an unobservant person might consider simple are in reality com- 

 plex ; and (2) that the ear (and by this term we mean, at present, ear, 

 nerve, and brain) has a power of analysis, or of resolving a compound 

 tone into its constituents. 



Physically, such a compound tone is built up of a fundamental or 

 prime tone, and of other tones known as over-tones, over-partial tones or 

 harmonics. Taking the tuning-fork (ut 2 ) in the series as the prime tone, 

 the partials are the following : — ( 



Number 

 Name 

 Note 

 Interval ratio 



l 

 Ut, 



c 



2 

 c' 



Octave 



3_ 



Fifth 



3 



,sw, 



9' 



4 



5 

 Mi, 



e" 



Fourth 



6 

 So! 4 



9" 



6"b 





etc. 

 etc. 

 etc. 



No. of vibs. 256 



512 



768 



Major Minor Minor Minor 



Third Third Third- Second - 

 1024 1280 1536 1792 2048 etc. 



The upper partials become more and more faint, and pass on to tones 

 making 9, 10, 11, etc., times the number of vibrations of the prime tone. 



Fig. 423. — Various forms of wave-curves. 



If we sound all these forks together, the motion is periodic but is com- 

 pounded of the motions represented by the waves of each of the partials ; 

 as, when two or more sources of sound move the air simultaneously, the 

 resulting disturbance must be the sum of what would be caused by each 

 source acting separately. The sensation, is that of a compound musical 

 tone having a period (and therefore pitch) of the lowest or prime tone. 

 The sensation, however, is not simple, but it is capable of analysis, when, 

 by an effort at attention, we sift out its constituents. This process of 

 resolution is easier for certain persons than for others, but even those 

 who are not musical soon develop the power. As well put by 

 Helmholtz, the power of analysis largely depends on attention. In 

 ordinary life it is not necessary thus to analyse compound tones, and 

 indeed it would be a distraction to do so, as our pleasure from musical 

 sounds does not spring from this analysis but from a general recognition 

 of their character, pitch, sequence, and harmony. 



Thus we find two classes of tones — (1) Those incapable of further 





