By far the greater part of these many pieces are independent of each other. Except in a few cases where Scarlatti, probably in his youth, followed the model of his father’s toccatas, he keeps quite clear of the suite cycle. The pieces have been called sonatas, but they are not for the most part in the form called the sonata form. This form (which is the form in which one piece or movement may be cast and is not to be confused with the sequence or arrangement of movements in the classical sonata) is, as we shall later have ample opportunity to observe, a tri-partite or ternary form; whereas the so-called sonatas of Scarlatti are in the two-part or binary form, which is, as we have seen, the form of the separate dance movements in the suite. Each ‘sonata’ is, like the dance movements, divided into two sections, usually of about equal length, both of which are to be repeated in their turn. In general, too, the harmonic plan is the same or nearly the same as that which underlies the suite movement, the first section modulating from tonic to dominant, the second back from dominant to tonic. But within these limits Scarlatti allows himself great freedom of modulation. It is, in fact, this harmonic expansion within the binary form which makes one pause to give Scarlatti an important place in the development of the sonata form proper. The harmonic variety of the Scarlatti sonatas is closely related to the virtuosity of their composer. He spins a piece out of, usually, but not always, two or three striking figures, by repeating them over and over again in different places of the scale or in different keys. His very evident fondness for technical formulæ is thus gratified and the piece is saved from monotony by its shifting harmonies. A favorite and simple shift is from major to minor. This he employs very frequently. For example, in a sonata in G major, No. 2 of the Breitkopf and Härtel collection of twenty sonatas[13] measures 13, 14, 15, and 16, in D major, are repeated immediately in A major. In 20, 21, 22, and 23, the same style of figure and rhythm appears in D major and is at once answered in D minor. Toward the end of the second part of the piece the process is duplicated in the tonic key. In the following sonata at the top of page seven occurs another similar instance. It is one of the most frequent of his mannerisms. The repetition of favorite figures is by no means always accompanied by a change of key. The two-measure phrase beginning in the fifteenth measure of the third sonata is repeated three times note for note; a few measures later another figure is treated in the same fashion; and in yet a third place, all in the first section of this sonata, the trick is turned again. Indeed, there are very few of Scarlatti’s sonatas in which he does not play with his figures in this manner.