The essential principle of binary form is the simplest conceivable. Every piece in binary form may be likened to a journey to a neighboring place, followed by a return home. “The King of France, with forty thousand men, marched up the hill, and then marched down again.” In the case of binary form, the king of France is the subject or theme of the piece; the forty thousand men are the variations or developments on this subject that are worked out as the piece proceeds; the hill is the progress from the tonic key to the contrasted tonal centre, generally the dominant, or, if the piece is in a minor key, its relative major; and the march down again is the return to the home key. More specifically, the first section begins with the announcement of the theme in the tonic key, and proceeds to ring changes upon it, meanwhile modulating to the contrasted key and ending with a firm and memorable cadence there. At this point the second section begins, with the theme as at first, but in the new instead of the original key; the modulation is reversed, the original key re-entered, and the same cadence already heard repeated, but now even more firmly, and with the added finality of the home key. The device is simplicity itself, yet it admits a surprising variety of detail within its perfectly obvious and satisfying unity of ultimate effect. Most of Bach’s allemandes, courantes, airs, sarabandes, and gigues, are executed in binary form.
The great disadvantage of this admirably concise and organic structure proved in the course of experience to be a certain monotony and rigidity. As movements became longer and more complex, the division into two sections, embodying but two keys in spite of momentary excursions to more remote centres, came to seem rather constricting. There was a dearth of variety about it, and a tendency to obviousness. The element of contrast, of adventure far afield, was somewhat lacking. Composers accordingly worked out, of course unconsciously, a more various but equally organic scheme of design—ternary form. In ternary form the first section is practically identical with that of binary form; but the second, instead of “marching down again,” makes the contrasting tonal centre it has reached but a starting-point for still further excursions. It modulates freely, using to the utmost the privilege of admission to all the keys of the gamut that music owes to Bach and his system of equal temperament; it plays with the theme, subjecting it to the modes of development we have already studied; it indulges in all sorts of pranks and whimsies, departing as much as possible from the set formality of the first section; in a word, it endeavors to establish a complete contrast with what has gone before, and while never violating logic, to get away as far as possible from the beaten track, from the rut of routine. Then, after this interregnum of variety, comes the third section with an emphatic reassertion of regularity, presenting once more the subject as at first, and in the tonic key, vindicating the unity of the movement of the whole, and rounding it out to orderly completeness. Splendid examples of this splendidly organic structure are most of the preludes, gavottes, bourrées, and minuets of Bach’s suites.
In the suite, then, as it was practiced by Bach and other seventeenth-century composers, we see operative a constantly broadening application of the use of expectation and fulfilment, in the interests of organic structure. Applying to artistic music those methods of metrical and harmonic form that had long determined the growth of folk-song and dance, the composers of this period gradually learned to make even wider and more intricate syntheses of their materials. So skilfully did they avail themselves of the relations between contrasting harmonic centres that they were able eventually to write whole movements as firmly organic, as deftly coordinated, as a vertebrate animal. By the ever-extending use of thematic variation and of free modulation, they made their pieces as various as they were systematic. And at last, in ternary form, they established that succession of statement, contrast, and reassertion, which seems even to-day the last word in the philosophy of general musical structure.
The gradual expansion and increase of complexity in the movements of the suite, made not only possible but logically necessary by the structural potencies of these great principles of statement, contrast, and reassertion, and of antithesis of keys, led eventually to a new phase of musical structure, the third and last in the evolution we have been tracing. The suite, in the seventeenth century the most successfully cultivated of all the forms of pure music, gave place in the eighteenth century to a still higher form, the sonata, which has held the position of supremacy ever since. The sonata form is, not only by tradition but by natural right, the norm of modern musical structure. Almost all the chief works of all the great composers from Haydn and Mozart to Brahms and Tschaïkowsky are cast in this mould, as we easily realize if we remember that not only those pieces specifically named “sonatas,” but also trios, quartets, quintets, and the like, and overtures and concertos and symphonies, are but pieces in sonata-form intended for various groups of instruments. The string quartet is a sonata for two violins, a viola, and a 'cello; the concerto is a sonata for solo instrument with orchestral accompaniment; and the symphony is a sonata on a large scale, for orchestra. This remarkable prevalence of a single type of structure in modern music means far more than the accidental survival, by inertia, of an artificial convention; it means that this type of structure is on the whole the best possible embodiment of variety and unity in tonal effects; that it is the natural outgrowth of more primitive forms; and that it is elastic enough to admit into its uniform scheme of order the most diverse expressions of individual temperaments and ideals. Tschaïkowsky’s intuition of beauty in tones is different enough from Haydn’s; and the formal medium of which both can avail themselves without violence to their genius must obviously be founded deep in universal human psychology.
The modern sonata consists, as a rule, of four movements, contrasted in character and in key, but combining to form a rational and complete whole. In expression, the movements conform deftly to the natural requirements of human nature. The first is energetic, vigorous, and complex. The second is sentimental, melancholy, noble, or profound. The third affords relief from the emotional concentration of the second; it is a dance, full of vivacity, humor, fantasy, and whimsical impulse; with Beethoven it becomes a consummate embodiment of the spirit of comedy, which is quite as essential a part of human nature as that of tragedy and earnest emotion. The fourth and last movement is again vigorous and dashing, but in a less intellectual way than the first; it ends the whole composition in a mood of simple and happy animation. As regards structure, moreover, the movements differ in conformity with the needs of the situation. The first, which is to be heard when the mind is most attentive and unfatigued, is by far the most complex,—is indeed often the only one in what is technically called “sonata-form.” The second, the interest of which is more emotional than intellectual, is usually of fairly primitive structure. The third, a dance, is in the simplest of ternary dance-forms, that of the minuet, and, as written by Haydn and Mozart, might almost be taken bodily out of a suite. The final movement is also usually of simple, obvious structure.
It is clear, then, that of all the movements of the sonata, the minuet is the nearest, in structure, to those more primitive types embodied in the suite.[28] It makes a link bridging the gap between the older form and its more highly-developed supplanter. A glance at its construction will show how near it is to those simple ternary forms already described in connection with the suite. The symphonic minuet of Haydn is built up out of phrases, welded together in the manner now so familiar to us.
