In the case of Scarlatti's sonatas, of course, one cannot yet speak of the classical sonata form, which was first developed by Haydn and Mozart. However, approaches to the sonata form are often recognizable. There are development-like passages, in some sonatas two musically contrasting themes, here and there clear codas, etc.
In Scarlatti's sonatas, there are several types of form:
1. The two-part forms
This is the basic form of most sonatas, in the sense of A - A '. However, a distinction must be made here between two types of form.
The type with one main motif
This is the most common type of form. A main motif, which often appears as an imitation in the second part, forms the essential musical material of an entire sonata. Often smaller motifs are derived from this main motif, which are then carried out in a sequence.
The type with two opposing main motifs
This type appears mainly at the beginning of the "Spanish" period, when Scarlatti confronted his own musical notions with the fascinating influences to which he was exposed. The contrasts that resulted from this are certainly extremely interesting. In some sonatas of this period, purely tonal parts without any transition are confronted with purely modal parts. As examples I will mention K105 and K107. From this confrontation, Scarlatti developed the idea of symbiosis, which led to intriguing results in later sonatas. Just as intriguing, however, are the examples just mentioned and other similar sonatas. It should now be clear that such an approach was extremely unusual for his own as well as for later times. At a time when Philippe Rameau's definition of tonality was making waves and was welcomed and understood as a new creed by almost every composer, Scarlatti was the one who deeply doubted this new definition. It could be that Scarlatti experienced the transition from modality to tonality as just as revolutionary as the composers of the post-war period saw the departure from tonality. His achievement lay in recognizing the new, but he combined this new with traditional values. The fact that this resulted in results that not a single other of his contemporaries could show should also give today's composers cause for thought.
As if to give extra emphasis to this duality, a great many sonatas are later laid out in pairs.
2. The three-part forms
In Scarlatti's wealth of forms, the three-part song form A - B - A is of course not missing. However, this form appears only a few times, namely in K202, K235, K273, or K282. The A-parts of K202 e.g. are fast, brilliant, playful and virtuoso. The contrasting B section, on the other hand, a pastoral and one of the deepest testimonies to the flamenco influence, represents a completely different world. However, this extreme contrast is masterfully combined into a unity. Especially the transition from the B part to the last A part is unique in its simplicity and conciseness. The harmonic turns of the B part are among the most extensive that Scarlatti has ever written. Some of the modulations in this section are so unusual that a parallel with Wagner comes to mind. The visionary faculties, which Scarlatti has in places, celebrates one of its highlights here.
In some sonatas such as K513 anticipates the three-movement structure of the later classical sonata, i.e. the multi-movement. This is about type A - B - C, in this case Andante - Allegro - Presto.
3. The four-part forma
The four-part form A - B - A - B that appears a few times, e.g. in K176 actually belongs to the category of the two-part form with two main motifs. Elements A and B are as opposite as they can be. In the case mentioned, the opposites consist of major-minor and andante-allegro. This A-B block is then repeated in a varied manner. So it is a further variation of the two-part type with two main motifs.
4. One-part Sonatas
Some of Scarlatti's sonatas are in one piece, such as K112. This sonata has no real half-ending. At the point of the half-close, the music simply continues without interruption.
In the chapters on the four creative periods, this matter is discussed in more detail.