On the Quality of Musical Sounds.
Hitherto we have treated only of simple sounds, that is to say, each sound has been considered to be of some one, and only one particular pitch. This is, however, far from being the case with the great majority of musical sounds we hear. If such sounds are attentively examined, almost all of them will be found to be compound; that is, each individual sound will be found to really consist of a number of simple sounds of different pitch. Those readers, who are not already practically cognizant of this fact, are strongly recommended to convince themselves of it, by experiment, before proceeding further. Some persons, both musical and unmusical, find great difficulty in distinguishing the simple elementary sounds, that form part of a compound tone. Those who experience any such difficulty, will find it useful to go carefully through the following experiments.
Strike a note on the lower part of the key-board of a pianoforte, say C|, in the Bass Clef. As the sound begins to die away, the upper octave of this note may, with a little attention, be readily distinguished. If the listener experiences any difficulty in recognising it, he will find it useful to lightly touch the 0 above (that is, the sound he is listening for) and let it die away before striking the Bass C|. If he does not then succeed, a resonator tuned to the expected sound, or, better still, two such resonators, one for each ear, should be used. By alternately applying these to, and withdrawing them from, the ears, even the most untrained observer cannot but detect the wished-for sound. Next, strike the same Bass C| as before, but