PROFESSOR AT HEIDELBERG 179 



prime tone and its first higher octave, according to whether 

 the condensation-maximum of the fundamental coincides with 

 that of the octave or not. Helmholtz endeavoured to decide 

 these questions by building up tones of different timbre by 

 the direct combination of simple tones produced according to 

 his own method with a tuning-fork. He selected the different 

 vowels of the human speech as a suitable object for imitation 

 because these can be produced as evenly sustained musical 

 tones. He had characterized these vowels (in writing to Bon- 

 ders) as sounds in which it is not the fundamental tone, but 

 one of the over-tones that is the strongest. He now adds the 

 more exact determination that o arises when the fundamental is 

 strongly accompanied by the higher octave, a weak accompani- 

 ment of the second and third tones producing an improvement 

 in the sound, while e is characterized by the third tone, with 

 moderate strength of the second, and the transition of o to e is 

 produced by diminishing the second tone, and letting the third 

 swell out, so that when both partials mentioned are given 

 strongly, o modified (o) arises. Thus he shows that the results 

 produced with the tuning-fork are confirmed by the investi- 

 gations of the tones of the human voice, at least when the 

 vowels are sung to a definite note. Since the vowel, as 

 pronounced, is a sound produced by the vibration of the 

 vocal cords, and the mouth, according to Helmholtz's theory, 

 acts as a resonator, which intensifies a given over-tone, 

 corresponding with a given vowel- sound, alteration in the 

 position of the mouth will produce given vowel-sounds from 

 the same musical sound. In order to demonstrate his vowel 

 theory, Helmholtz constructed little glass bulbs as resonators 

 with two openings, one of which was prolonged into a short 

 funnel-shaped neck to be inserted into the ear. Then, on 

 sounding the proper tone outside, the mass of air within the 

 sphere vibrated in sympathy, and thus acted on the ear. With 

 these resonators it was easy not only to demonstrate most 

 of the acoustic phenomena, such as objective combinational 

 tones, over-tones, and their beats, but also to establish the 

 accuracy of the vowel theory. Further, it was proved that 

 musical timbre depends solely on the presence and intensity 

 of the partial tones contained in the musical tone, and not in 

 their different phases, although this is only certain where the 



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