Sonata in d K1 L366

The most important part of Scarlatti's oeuvre is his 555 surviving harpsichord sonatas. The Essercizi of 1739 and few other sonatas published during his lifetime established his fame and influenced the works of other composers such as Johann Sebastian Bach (Fantasia in C minor BWV 906, Goldberg Variations), Jacques Duphly, Pietro Domenico Paradies or Muzio Clementi. Handel is a special case, as he and Scarlatti met personally in their youth and possibly influenced each other. On the Iberian Peninsula, a separate 'school' of keyboard virtuosos emerged, including Carlos Seixas, Antonio Soler, José de Nebra, among others.

The unpublished sonatas have not survived as autographs, but are only available as copies, which were collected in various volumes from 1742 and especially during the last years of Scarlatti's life from 1749 to 1757, so apart from stylistic features they give no clear indication of the time of composition. The most important collection of manuscripts is now in the Biblioteca Nazionale Marciana in Venice (496 sonatas): These 15 volumes in red morocco leather each have the united arms of the kingdoms of Portugal and Spain in gold on the cover and probably belonged to Queen Maria Bárbara (See illustration). They are all dated. Simpler but important manuscripts are in the Biblioteca Palatina (Conservatorio Arrigo Boito) in Parma (463 sonatas), in the University Library of Münster (349 sonatas), and in the Library of the Gesellschaft der Musikfreunde in Vienna (308 sonatas; formerly owned by Johannes Brahms).

Ralph Kirkpatrick was the first to notice that in the Venice and Parma volumes from 1749 onwards, two sonatas of the same key almost invariably follow one another, or that they differ only in the tonal gender; there are also extensive similarities between the two manuscript collections (and in some cases other sources).