II. ESSENTIALS OF SONATA-FORM.
The element of true novelty in sonatas is to be found, not in these primitive movements, but rather in those movements which are in "sonata-form," and which show a breadth of conception and an elaboration in development never found in simple lyric forms like the minuet. This breadth and elaboration is always the result of a germination of musical thought, such as we have already often mentioned, and by virtue of which alone a composition can take on real grandeur of proportions. The essentials of sonata-form are (1) the presentation of two or more themes or subjects in that section known as the Exposition, and symbolized in our diagrams by the letter A; (2) the evolution of these themes, by means of melodic germination, in that section known as the Development, and symbolized by B; and (3) the restatement of the original themes, rounding out the movement symmetrically, in the section known as the Recapitulation, and symbolized again by A on account of its practical identity with the Exposition. It matters not which movement of a sonata takes this characteristic form, whether, as in the majority of cases, it is the first (whence the term "first-movement form," often used as a synonym for "sonata-form") or the slow movement, as often happens, or the finale. Wherever sonata-form exists we find this three-part sectional structure, resulting from the natural germination in the middle section of the musical ideas stated in the first, followed by their restatement in the third section.
The reader may ask at this point, in what respect such a form differs from the simple ternary form illustrated in a minuet, for example, wherein the second section usually contains some development of the theme, and the third some recapitulation. The answer is that in the sonata-form the enlargement of the proportions throughout results, first, in the substitution of complete and more or less contrasting themes, for the rather slight musical subject of a minuet, and second, in the substitution of a long and elaborate development of these themes for the rather casual and superficial modification of the subject which forms the second section of a minuet. Moreover, in the sonata-form a novel feature is the contrast introduced by making the first section embody duality of key (first theme in tonic, second in related key) while the third section, by presenting both themes in the tonic, embodies unity of key. Nevertheless it remains true that sonata-form is, both logically and historically, a development of such simple forms as we have in the minuet, as is indicated by the name of "developed ternary form" often given to it.[22]
Sonata-form is thus but an extreme application of certain essential principles of structure exemplified in simple ways in other more primitive musical forms, and for that matter in many other departments of life. It is perhaps not over-fanciful to discover the same principles in the construction of a novel, in which we often find: first, the presentation of certain characters, more or less in antagonism; second, the development of the plot and of the characters themselves; and third, the reconciliation of the characters in the denouement. Similarly, a sermon consists of (1) the assertion of a text or subject of discourse, (2) the illustration of its truth by examples and other elucidations of what is implied in it, and (3) a final restatement of it with the greater force made possible by its discussion. Or again, we may see striking analogies to the artistic form we are considering in such processes of nature as the budding, flowering, and death of a plant, or in human life with its youth, its period of activity, and its time of retrospect.