=Structure of Beethoven’s Sonatas=.—With such resources at his command, Beethoven was able to give a fuller scope to the Sonata than was formerly possible, filling out each movement, and perfecting it for the expression of an integral part of the general idea, and finally placing it in its proper relationship to the whole. The Sonata Form, as settled by Haydn, was made the point of departure, serving almost invariably as the basis of the first movement, and frequently, in shortened form, for the second, generally slow, movement. For the third movement, Beethoven at first employed the Minuet, following the custom in the symphonies of Haydn and Mozart; but later this was generally omitted in the pianoforte sonatas, while in the symphonies its time was quickened into that of the dainty, sparkling Scherzo. For the finale, the Rondo form was most frequent; though, in order to give a fuller compass to the thought, a combination of the Rondo and Sonata forms was invented by Beethoven, and used even in his first sonatas. The Rondo form also appeared occasionally in the slow movement. Add that other forms, notably that of the Variation, sometimes supplanted one or the other of these, and we have the structure generally followed by Beethoven. =Unity of Conception=.—All these movements were associated in an organic unity of conception which made one grow out of another with perfect naturalness. Sometimes, indeed, as in opus 27, a continuity of performance was indicated; always, however, the feeling of dependence of one movement upon another is present; so that the criticism made upon Haydn’s symphonies, that a movement of one could be interchanged with a similar movement of any other without perceptible difference, could never be made with regard to Beethoven’s works. =Key Relationship=.—In key relationship, Beethoven struck out from stereotyped paths, frequently using _contrasting keys related to the third of the initial chord_; thus a movement or passage in C major might be followed by any key related to E, the third of the chord of C, such as E or A major or minor. The original key was most widely departed from in the slow movement, where the beauty of contrast was exceptionally noticeable. =Number of Movements=.—The number of movements which he adopted was at first four, but this afterwards varied considerably, two or three movements prevailing; while in the fantasie-sonatas, and especially in the last five sonatas, an indefinite number of movements, some of them very short, appeared. He explained this discrepancy on the ground that he adapted the number of movements to his thought; and when he felt that he had given complete expression to this, the sonata was brought to a close.