What Scarlatti is most prominently remembered for are the 556 short keyboard sonatas originally labelled Essercizi (Exercises). When he died in Madrid, Scarlatti left this treasury of manuscripts, which were largely unplayed beyond Spain and Portugal until pianist Carl Czerny published a selection of the sonatas in 1839.
Subsequently, an ostensibly complete set of sonatas was ordered and numbered by Luigi Longo (whose numbers begin with the initial “L”) in 1906.
Ralph Kirkpatrick added to and reorganized the sonatas (designating them with a second numbering system with the initial “K”) in a 1953 critical edition considered de rigueur for Scarlatti performance.
It is thought that many of Scarlatti´s 555 sonatas were envisioned in pairs, contrasting and complementing each other with regard to tonality, dynamics, tempo, complexity etc.
The result is an almost inexhaustible collection of pieces, the artistic value of which cannot be overestimated.