HARMONY IN MUSIC. 95 



above, and listen attentively to the sound of the piano as 

 it dies away. If this l>' J7 is a real upper partial in the 

 compound tone uttered by the singer, the sound of the 

 piano will apparently not die away at all, but the corre- 

 sponding upper partial of the voice will be heard as if 

 the note of the piano continued. 1 By properly varying 

 the experiment, it will be found possible to distinguish 

 the vowels from one another by their upper partial tones. 

 The investigation is rendered much easier by arming 

 the ear with small globes of glass or metal, as in Fig. 12. 



FIG. 12. 



The larger opening a is directed to the source of sound, 

 and the smaller funnel-shaped end is applied to the drum 

 of the ear. The enclosed mass of air, which is almost 

 entirely separated from that without, has its own proper 

 tone or key-note, which will be heard, for example, on 

 blowing across the edge of the opening a. If then this 

 proper tone of the globe is excited in the external air, 

 either as a fundamental or upper partial tone, the in- 



1 In repeating this experiment the observer must remember that the e & 

 of the piano is not a true twelfth below the i'fe. Hence the singer should 

 first bo given b' (2 from the piano, which he will naturally sing as b &, an 

 octave lower, and then take a true fifth below it. A skilful singer will 

 thus hit the true twelfth and produce the required upper partial b' t. On 

 the other hand, if he sings eh from the piano, his upper partial b'\i will 

 probably beat with that of the piano. TB. 



