Of Scarlatti’s 555 sonatas, about 10 are for violin and continuo, 3 are specifically for organ, and the rest are for harpsichord. Although a few of the early sonatas, such as those for violin, consist of up to four movements, the bulk are single movements, normally in two sections. They either contrast slow movements with fast ones, couple complementary fast movements, or extend the total tonal range of a pair conceived as a unit.