pages: practicalmagicia00harr.pdf, 87
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practicalmagicia00harr.pdf | 87 | THE PRACTICAL MAG:CIAN. 77 distinctions of pitch, loudness, and quality, by the ordinary ac- tions of the vocal organs. In ordinary language, we speak of noise, of common sound, and of musical sound-terms employed by Dr. Thomas Young in illustrating the mechanical agencies of articulation A quill striking against a piece of wood causes a noise, but striking successively against the teeth of a wheel, or of a comb, a continued sound, and, if the teeth of the wheel are at equal distances, and the velocity of the rotation is constant, a musical sound. The general terms-pitch, loudness, quality, and duration, embrace all the distinctions with which the musician has to deal, and which he uses in his art." The distinguishing feature of musical sound is its uniform pitch througliout its duration, and acoustically musical sound is composed of an equal number of impulses or noises produced in equal tones. The general terms-pitch, loudness, quality, and duration, also embrace all the distinctions heard in ordinary sounds. These sounds differ from the musical in the pitch constantly varying throughout their duration, as the human voice in speaking, and the voice of quadrupeds. Acoustically such sounds are composed of an unequal number of impulses or noises produced in equal tones. And from this circumstance pitch, in the strictly musical sense, is not a property of ordinary sound. The general erms-loudness and quality, embrace all the dis- tinctions heard in a noise, as in the collision of two unclastic sticks. Pitch and duration can scarcely be considered as belong- ing to common noise. Thus we have-(1) noise whose audible distinctions are comprehended under the general terms loudness and quality ; (2) common sound, whose audible distinctions are comprehended under the general erms-loudness, quality, duration, and every varying pitch (3) musical sound, whose audible distinctions are comprehended under the general terms- loudness, quality, duration, and uniform pitch. Phonation, or the production of voice, is a result of actions taking place under two distinct classes of laws-namely, the or- dinary mechanical laws of acoustics, and the physiological laws of muscular movement. Tbe adjustment of the vocal mechanism to be brought into operation by the current of air, is made by actions under the latter laws and phonation is the result of the reaction of the mechanism on the current of air, by mechanical movements under the former laws Now, the pitch of the voice essentially depends on the tension of the vocal ligaments ; the loudness or the extent of the excursion of these ligaments in their vibration ; the duration on the continuance of the vocalizing causes ; the quality on the organization of the larynx, and also on the form and size of the vocal tube. The form and size of this tube can be altered in various ways-for instance, by dilating |