PHRASE-ADDITION.—The phrase is the structural basis of all musical composition. By this is meant, not necessarily the single phrase, but the phrase in its collective sense.
The phrase is, after all, only a unit; and the requirements of Variety cannot be wholly satisfied by the mere development and extension of a single phrase, except it be for a certain limited section of the piece, or for a brief composition in small form (like Schumann, op. 68, No. 8).
The act of addition does therefore enter into the processes of music-writing, as well as extension. Phrase may be added to phrase, in order to increase the primary material, and to provide for greater breadth of basis, and a richer fund of resources. The condition to be respected is, that such aggregation shall not become the ruling trait, and, by its excess, supplant the main purpose,—that of development. That is, it must be held rigidly within the domain of Unity. The student of the classic page will therefore expect to find a more or less marked family resemblance, so to speak; prevailing throughout the various phrases that may be associated upon that page.
Each additional phrase should be, and as a rule will be, sufficiently "new" in some respect or other to impart renewed energy to the movement; but—so long as it is to impress the hearer as being the same movement—there will still remain such points of contact with the foregoing phrase or phrases as to demonstrate its derivation from them, its having "grown out" of them.
This process of addition (not to be confounded with the methods of extending a single phrase, illustrated in the preceding chapter) is exhibited first, and most naturally, in the so-called Period-form.
THE PERIOD.—The Period-form is obtained by the addition of a second phrase to the first. It is therefore, in a sense, a double phrase; that is, it consists of two connected phrases, covering eight ordinary measures, or just double the number commonly assigned to the single phrase.
Each one of these phrases must, of course, have its individual cadence, or point of repose; the first—called the Antecedent phrase—has its cadence in the fourth measure, and the second—called the Consequent phrase—in the eighth measure. The effect of the Period-form is that of a longer sentence interrupted exactly in the middle,—not unlike a bridge of two spans, resting on a central pier. But, precisely as the central pier is only an intermediate point of support, and not terra firma, so the ending of the Antecedent phrase is never anything more weighty than a semicadence, while the definite, conclusive, perfect cadence appears at the end of the Consequent phrase,—or of the entire period-form.
The reason for this distinction of cadence is obvious. A period is not two separate phrases, but two related and coherent phrases which mutually balance each other. The Consequent phrase is not merely an "addition" to the first, but is its complement and "fulfilment." The two phrases represent the musical analogy of what, in rhetoric, would be called thesis and antithesis, or, simply, question and answer. In a well-constructed period the Antecedent phrase is, therefore, always more or less interrogative, and the Consequent phrase responsive, in character.
For illustration (Mendelssohn, No. 28):—