742 SPECIAL SENSES. 



most pleasing effects, to change the tonic, by what is called modulation, re- 

 turning afterward to the original key. 



Quality of Musical Sounds. Nearly all musical sounds, which seem at 

 first to be simple, can be resolved into certain well defined constituents ; but 

 with the exception of the notes of great stopped pipes in the organ, there are 

 few absolutely simple sounds used in music. These simple sounds are pure, 

 but are of an unsatisfactory quality and wanting in richness. Almost all 

 other musical sounds have a fundamental tone, which is at once recognized ; 

 but this tone is accompanied by harmonics caused by secondary vibrations of 

 subdivisions of the sonorous body. The number, pitch and intensity of these 

 harmonic, or aliquot vibrations affect what is called the quality, or timbre of 

 musical notes, by modifying the form of the sonorous waves. A string vi- 

 brating a certain number of times in a second, if the vibrations were abso- 

 lutely simple, would produce, according to the laws of vibrating bodies, a 

 simple, musical tone ; but as the string subdivides itself into different por- 

 tions, one of which gives the 3d, another, the 5th, and so on, of the funda- 

 mental tone, it is evident that the form of the vibrations must be consid- 

 erably modified, and with these modifications in form, the quality, or timbre 

 of the note is changed. 



From what has just been stated, it follows that nearly all musical notes 

 consist, not only of a fundamental sound, but of harmonic vibrations, sub- 

 ordinate to the fundamental and qualifying it in a particular way. These 

 harmonics may be feeble or intense ; certain of them may predominate over 

 others ; some that are usually present may be eliminated ; and in short, there 

 may be a great diversity in their arrangement, and thus the timbre may pre- 

 sent an infinite variety. This is one of the elements entering into the com- 

 position of notes, and it affords a partial explanation of quality. 



Another element in the quality of notes depends upon their re-enforce- 

 ment by resonance. The vibrations of a stretched string not connected with 

 a resonant body are almost inaudible. In musical instruments the sound is 

 taken up by some mechanical arrangement, as the sound-board of the organ, 

 piano, violin, harp or guitar. In the violin, for example, the sweetness of 

 the notes depends chiefly upon the construction of the resonant part of the 

 instrument, and but little upon the strings themselves, which latter are 

 frequently changed ; and the same is true of the human voice. 



In addition to the harmonic tones of sonorous bodies, various discordant 

 sounds are generally present, which modify the timbre, producing, usually, a 

 certain roughness, such as the grating of a violin-bow, the friction of the 

 columns of air against the angles in wind-instruments, etc. All of these 

 conditions have their effect upon the quality of tones ; and these discordant 

 sounds may exist in infinite number and variety. These sounds are composed 

 of irregular vibrations and consequently are inharmonious. Nearly all notes 

 that are spoken of in general terms as musical are composed of musical, or 

 harmonic, aliquot tones with the discordant elements to which allusion has 

 just been made. 



Aside from the relations of the various component parts of musical notes, 



