are the two vital requisites upon which the enjoyment of any art depends. The artist's utterances or creations must be intelligible, and they must be interesting. The lack, partial or total, of either of these qualities neutralizes the force of the intended impression, in precise proportion to the default.
In musical composition these two requisites are embodied in the principles of Unity and Variety.
Unity—in its various technical phases of Uniformity, Regularity, Similarity, Equality, Agreement, or whatever other synonym we may find it convenient to use—is the condition out of which the composer must secure intelligibility, clearness, definiteness of expression. Glance at Ex. 2, and note the evidences of unity (similarity) in the rhythmic and melodic formation of the first four measures.
Variety—in its most comprehensive application—is the medium he must employ to arouse and sustain the hearer's interest. Glance again at Ex. 2, and note the contrast between the two halves of the first four measures, and between these and the following two measures.
These conditions are, of course, squarely opposed to each other, though their interaction is reciprocal rather than antagonistic; and, from what has been said, it is obvious that they are of equal importance. Hence, as was declared on the second page, the great problem of the art-creator consists in so balancing their operations that neither may encroach upon the domain of the other. For too constant and palpable Unity will inevitably paralyze interest; while too much Variety will as surely tend to obscure the distinctness of the design.
The workings of the principle of Unity (to which attention must first be given, because it appears to come first in the order of creation) are shown in the following elementary details of composition:—
(1) Music is not an art that deals with space, but with Time; therefore the units of its metrical structure are not inches and the like, but divisions of time, the basis of which is the beat. The principle of Unity dictates that the beats which are associated in one and the same musical sentence shall be of equal duration. Every musician admits the necessity of keeping "strict time"—that is, marking the beats in regular, equal pulses. The sub-divisions of the beats (for example, the eighth or sixteenth notes within a beat) must also be symmetric. So imperative is this law that it generally prevails through the entire piece, with only such temporary elongations or contractions (marked ritardando or accelerando) as may be introduced for oratorical effects.
(2) The beats are grouped in measures of uniform duration; that is, containing equal numbers of beats.
(3) The natural accent falls upon the corresponding beat, namely, the first, of each measure; therefore it recurs regularly, at uniform intervals of time.
(4) The melodic contents of the first measure, or measures, are copied (more or less literally) in the next measure, or measures; and are encountered again and again in the later course of the piece, thus insuring a fairly uniform melodic impression from which the character and identity of the composition are derived. Turn to the 8th Song Without Words of Mendelssohn, and observe how insistently the figure
[Illustration: first fragment of 8th Song]
and its inversion
[Illustration: second fragment of 8th Song]
run through the whole number.
(5) The specific figure of the accompaniment is usually reproduced from measure to measure (or group to group) throughout whole sections of the piece. Observe, in the 37th Song Without Words, how constantly the ascending figure of six tones recurs in the lower part (left hand). Glance also at No. 30; No. 1; No. 25. Many other evidences of Unity are invariably present in good music, so naturally and self-evidently that they almost escape our notice. Some of these are left to the student's discernment; others will engage our joint attention in due time.
In every one of these manifestations of unity there lies the germ of the principle of Variety, which quickens into life with the action of the former, always following, as offspring and consequence of the primary unity. Thus:—
(1) The beats, though uniform in duration, differ from each other in force. The first pulse in each measure (or metric group of any size) is heavier, stronger, than the following. It—the first—is the "impulse," and is what is called the accent. This dynamic distinction it is that gives rise to the two fundamental classes of rhythm, the duple and triple. In duple rhythm the accent is followed by one unaccented or lighter beat, so that regular alternation of heavy and light pulses prevails incessantly. In triple rhythm the accent is followed by two lighter beats, creating similarly constant, but irregular alternation of heavy and light pulses.
[Illustration: Duple and Triple Rhythm]
This distinction is so significant and so striking, that the music lover who is eager to gain the first clues to the structural purpose of a composition, should endeavor to recognize which one of these two rhythmic species underlies the movement to which he is listening. It is fairly certain to be one or the other continuously. Of duple measure, the march and polka are familiar examples; of triple measure, the waltz and mazurka. The "regularity" of the former rhythm imparts a certain stability and squareness to the entire piece, while triple rhythm is more graceful and circular in effect.
(2) The same dynamic distinction applies also to whole measures, and
(3) to accents. The first of two successive measures, or of two or more accents, is always a trifle heavier than the other.
(4) The melodic contents of the first measure may be exactly reproduced in the succeeding measure; but if this is the case, they are very unlikely to appear still again in the next (third) measure, for that would exaggerate the condition of Unity and create the effect of monotony.
[Illustration: Example 1. Fragment of Folk-song.]
The measure marked b is exactly like a. But c is all the more contrasting, on account of this similarity.
Or, the melodic contents of a measure may be thus reproduced, as far as the rhythm and direction of the tones are concerned, but—for variety—they may be shifted to a higher or lower place upon the staff, or may be otherwise modified.
