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Next to rhythm, modulation is the most stimulating and enchanting element in music. No composition of any scope can be considered truly great unless it abounds in beautiful modulations. Certain composers, to be sure, have in this respect more genius than others—notably Schubert, Chopin, Wagner and Franck whose music seems to waft us along on a magic carpet of delight. But just as Unity depends upon a definite basic tonality, so Variety is gained by this very freedom of modulation. Without it is monotony; with too much modulation, an irritating restlessness. By the perfect balance in his works of these two related elements a genius may be definitely recognized.
The simplest and on the whole most frequent type of musical sentence or period consists of eight measures, subdivided into two balancing phrases of four measures[51] each—the component parts plainly indicated by various cadences and endings soon to be explained. These four-measure phrases are often, though not invariably, still further subdivided into two sections of two measures each. Let us now corroborate these statements by an examination of the opening sentence of the Scherzo of Beethoven's Second Sonata for Pianoforte. This concise sentence is an epitome of the chief principles of organic musical expression. At the outset[52] we see the leading motive, which consists of an ascending broken chord twice repeated. We see also
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the first phrase of 4 measures and the second phrase[53] of similar length, alike subdivided into two sections of 2 measures each. In the third measure we find a modulation into the dominant key (indicated by the D-sharp) and in the fourth measure a cadence with a feminine ending in this key. The second—or after—phrase corresponds exactly to what has gone before: we have the same repetition of the motive in a different part of the scale; and finally, in the 8th measure, a cadence in the home key, also with feminine ending.
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When the sentence is played, it is evident how unsatisfactory would be the effect if a complete stop were attempted at the 4th measure; and how symmetrical and convincing is the impression when the eight measures are considered an unbroken sweep of musical thought.[54] There are, in fact, a few complete compositions in musical literature which contain but a single sentence of eight measures. As an example may be cited the song from Schumann's Lieder Album für Jugend, op. 79, No. 1. (See Supplement No. 19.) For purposes of practical appreciation[55] it is enough to state that a cadence is an accepted combination of chords (generally the tonic, dominant and subdominant) which indicates that some objective, either temporary or final, has been reached. When the dominant chord or any dominant harmony is immediately followed by the tonic the cadence is called perfect or final, and may be compared to a period in punctuation, e.g.