The larger, broader, or "higher" designs of musical composition are divided into two classes: the three Rondo-forms, and the two Sonata-allegro forms. The latter constitute the superior of the two classes, for the following reasons:—
In the first place, the rondos rest upon a narrower thematic basis, centering in one single theme—the Principal one—about which the other themes revolve. Further, their most salient structural feature is nothing more significant than simple alternation (of the Principal theme with its one or more Subordinates) the Principal theme recurs after each digression with a persistence that lends a certain one-sidedness to the form,—only excepting in the Third (and highest) Rondo-form, which, by virtue of its broad Recapitulation of the first Division, approaches most nearly the rank of the Sonata-allegro design, as will be seen.
In the Sonata-allegro forms, on the other hand, the leading purpose is to unite two co-ordinate themes upon an equal footing; one is to appear as often as the other; and the two themes together constitute the thematic basis of the design. These are, as in the rondos, a Principal theme (called principal because it appears first, and thus becomes in a sense the index of the whole movement), and a Subordinate theme (so called in contradistinction to the other),—contrasting in character, as usual, but actually of equal importance, and of nearly or quite equal length. To these, there is commonly added a codetta (or "concluding theme" as it is {122} sometimes called, though it seldom attains to the dignity of a theme),—sometimes two, or even more, codettas, which answer the general purpose of a coda, rounding off and balancing this Division of the design. This union of the two or three thematic components that are to represent the contents of the design, is the Exposition, or first Division, of the Sonata-allegro forms. It indicates a point of contact between the latter and the rondo,—in the Third form of which we also find an Exposition. Careful comparison of the two types of exposition reveals the significant difference between the two classes, however; in the Third Rondo, the exposition was an alternation of themes, with decided preference for the principal one; in the Sonata-allegro it is a union of themes, without preference, resulting in a broader thematic basis.
THE SONATINE FORM.—In the Sonatine-form, or the smaller variety of the sonata-allegro designs, this Exposition (or first Division) is followed at once,—or after a few measures of interlude, or re-transitional material,—by a Recapitulation of the Division, as was seen in the Third Rondo-form, and under the same conditions of transposition as there. The diagram of the form is therefore as follows:—
| Exposition | Very brief Inter- lude | Recapitulation | ||||
| Pr. Th. | Sub. Th. | Codetta | Pr. Th. | Sub. Th. | Codetta | |
| As usual. | In some related key. | Optional | As before. | In the principal key. | Also in principal key. | |
An additional coda is, as usual, likely to appear at the end.
This diagram should be very carefully compared with that of the Third Rondo-form on page 119, and the points both of agreement and dissimilarity noted. More minute details of the Sonatine form will be given in the next chapter, in connection with the larger and more fully developed Sonata-allegro form.
An illustration of the Sonatine-form will be found in Mozart, 6th pianoforte sonata, adagio. Number the measures, as usual, and analyze with reference to the indications given; the figures in parenthesis again denote the measures.
Principal Theme, B-flat major, period-form,—possibly double-period, because of the slow tempo and large measures (1-8). There is no Transition.
Subordinate Theme, F major, period-form, extended. Antecedent (9-12); consequent, very similar (13-16); extension by addition of new phrase, as in the group-form (16 1/2-19).