The Effects of Rhythm and of Harmony Illustrate the Same Principle -- What Causes Loudness and Pitch of Tone -- What Causes Quality -- Musical Tones Compounded of Partial Tones Caused by Vibrations Related as 1:2, 2:3, etc. -- These Partial Tones are Merely Repeated in Scales -- And Chords -- Musical Harmony Results from Putting Together Notes Having Like Partial Effects -- This True of the Most Complex Arrangements -- True of Poetic Harmony.
AS stated on page 334, the most important difference between the effects of rhythm and of musical harmony is found in the fact that, in the latter, the mind is not directly conscious, as it is in the former, of divisions or subdivisions in time. It is conscious merely of an agreeable thrill or glow. That this thrill is experienced in the degree in which the divisions are alike, or are multiples of those that are alike, is a scientific discovery.
The chief facts with reference to the subject for which we are indebted to science are, first, that degrees of loudness are determined by the relative amplitude of vibrations. A string of a certain texture and length will produce a loud sound in the degree in which it is struck violently, and, therefore, caused to cover a greater space with its vibrations. The second fact is, that degrees of pitch are determined by the relative time of vibrations. A string shortened in length, and therefore vibrating more rapidly, will produce a higher tone. It is from this fact, that, by very simple experiments, the law