Chapter X: The Three-Part Song-Form

DISTINCTION BETWEEN BIPARTITE AND TRIPARTITE FORMS.--We learned, in the preceding chapter, that the Two-Part Song-form is a composition of rather brief extent, with so decisive a perfect cadence in its course as to divide it, in a marked manner, into two separate and fairly individual sections or "Parts."

Between this and the next higher form,--that with _three_ such Parts,--there is a distinction far more essential and characteristic than that of mere extent; a distinction that does not rest simply upon the number of Parts which they respectively contain. Each of the two classes of formal design, the Two-Part and the Three-Part, embodies a peculiar structural idea; and it is the evidence of these respective ideas,--the true content of the musical form,--which determines the species. The "number" of sections is, in this connection, nothing more than the external index of the inherent idea.

The Two-Part forms embody the idea of _progressive growth_. To the first Part, a second Part (of similar or related melodic contents) is added, in coherent and logical succession. It should not be, and in good clear form it is not, a purely numerical enlargement, for the association of the second Part with a foregoing one answers the purposes of confirmation and of balance, and is supposed to be so effectuated as to institute and maintain unity of style, and some degree of progressive development. But the second Part, in this bipartite design, does little or nothing more, after all, than thus to project the musical thought on outward in a straight line (or along parallel lines) to a conclusion more or less distant from the starting-point,--from the melodic members which constitute the actual germ, or the "text" of the entire musical discourse. A very desirable, not to say vital, condition is therefore {90} lacking, in the Two-Part forms; namely, the corroboration of this melodic germ by an emphatic return to the beginning and an unmistakable re-announcement of the first (leading) phrase or phrases of the composition.

Nothing could be more natural than such corroboration. Any line of conduct, if pursued without deviation, simply carries its object farther and farther away from its origin. If, as in the circle, this line is led back to the starting-point, it describes the most satisfying and perfect figure; it perfects, by enclosing space. Whereas, if it goes straight onward, it ultimately loses itself, or loses, at least, its connection with its beginning and source.

Nowhere is this principle of _Return_ more significant and imperative than in music, which, because of its intangibility, has need of every means that may serve to define and illuminate its design; and hence the superior frequency and perfection of the Three-Part form, _which, in its Third Part, provides for and executes this Return to the beginning_. Its superiority and greater adaptability is fully confirmed in the practice of composition; the number of Three-Part forms exceeds the Two-Part, in musical literature, to an almost surprising degree; and it may therefore be regarded as the design peculiarly adapted to the purposes of ordinary music writing within average limits.

The three successive divisions of the Three-Part Song-form may then be characterized as follows:--

PART I.--The statement of the principal idea; the presentation of the melodic and rhythmic contents of the leading thought, out of which the whole composition is to be developed. It is generally a period-form, at least, closing with a firm perfect cadence in the principal key, or one of its related keys.

PART II.--The departure (more or less emphatic) from this leading melodic statement. It is, for a time, probably an evident continuation and development of the melodic theme embodied in the First Part; but it does not end there; it exhibits a retrospective bent, and--when thoroughly legitimate--its last few measures prepare for, and lead into, the melodic member with which the piece began. Its form is optional; but, as a rule, decisive cadence-impressions are avoided, unless it be the composer's intention to _close_ it with a perfect cadence (upon any _other_ than the principal tonic), and accomplish the "return to the beginning" by means of a separate returning passage, called the Re-transition.