Omitting a few rare exceptions, such as the Finale of the Hammerclavier Sonata, we may say that all movements in so-called Classical form represent some definite stage in this line of evolution. No doubt experiments were tried by Schumann and Chopin and other composers of the Romantic School, but even these are not so much new discoveries as variants of the established type, sometimes due to carelessness or indifference, and sometimes to deliberate plan. It must be remembered that the generation which succeeded Beethoven paid much less attention to structure than to expression. The essays of Berlioz and Schumann, admirable in most respects, are almost entirely silent on the subject of musical form, and their work, considered from this standpoint, is not an advance but a retreat. Schumann, of course, was far the greater of the two; yet even with him we feel that deliberation has not always brought counsel. The introduction to his A minor Quartett, and still more the first movement of his C major Symphony, are really steps away from organism, condoned in part by undeniable beauties of style, but at the same time needing condonation as structural errors. Even in the shorter narrative forms of ballade and impromptu, of fantasia and novellette, the same rule holds good. Their structure will be found satisfactory in proportion as it is organic, it will be found organic in proportion as it conforms to this law of natural development.
There remains a word to be said about the combination of different numbers or movements into a continuous work. The complete sonata-form, like the Trilogies or Tetralogies of the classical drama, is a complex organism of which each part is itself organic, a corporate body composed of separate but interdependent members. Hence we should naturally expect that in the earliest examples there would be a comparative homogeneity of melodic style and key system, and that this homogeneity would be gradually differentiated as the form advanced towards perfection. This is precisely what has happened. In the first pianoforte sonata of Haydn all the movements are in the same key, as they were in the suites and partitas of a previous age; then, by steps which are readily traceable, the form progressed and developed until it reached its structural climax in Brahms. So also with the style of the work as a whole, by which is meant the selection of different organic types in its constituent members. Out of all possible alternatives--the minuet, the rondo, the air with variations, the fully-developed 'ternary' form--it is clearly the composer's business to choose specimens which will afford the most complete contrast and yet combine into the most organic unity. The gradual application of this rule is simply another name for the growth of the sonata form. One has only to compare Haydn's first quartett with one of the Rasoumoffskys to see the advance; one has only to compare the _Eroica_ Symphony with Chopin's B-flat minor Sonata to see the retrogression. In this, as in other respects, Brahms has restored the balance and has adapted the traditions of Beethoven to the language of the present day.