Op. 120, first movement.
Op. 147, first movement (in the Recapitulation, the principal theme is transposed).
Op. 164, first movement (the same).
Beethoven, symphony, No. 5, first movement.
Symphony, No. 1, first Allegro; also the second movement; and the Finale.
CHAPTER XVIII. IRREGULAR FORMS.
CAUSES.—Despite the many points of resemblance between the various forms to which our successive chapters have been devoted,—the natural consequence of a continuous line of structural evolution to which each plan owes its origin,—they are separate and independent designs, with individual character and purpose; so much so, that the composer may, and usually does, select and apply his form according to the purpose which he has in view. But the form is made for the music, not the music for the form; no serious composer writes music for the sake of the form, but chooses the form merely as a means to an end. The highest ideal of structural dignity and fitness is, to work from the thematic germ outward, and to let the development of this germ, the musical contents, determine and justify the structural plan and arrangement.
But the aims of the composer outnumber the regular forms, and therefore modifications are unavoidable, in order to preserve the latitude which perfect freedom of expression demands. The student may rest assured of the existence of many irregular species of these fundamental forms (as exceptions to the rule) and must expect to encounter no little difficulty and uncertainty in defining the class to which his example belongs,—until wider experience shall have made him expert.
All such irregular (or, in a sense, intermediate) varieties of form must necessarily either admit of demonstration as modification of the regular designs; or they will evade demonstration altogether, as lacking those elements of logical coherence which constitute the vital and only condition of "form and order" in musical composition.