percussion instrument of the clapper family, consisting of two hollowed-out pear-shaped pieces of hardwood, ivory, or other substance hinged together by a cord. Castanets are usually held in the hand and struck together. They are played in differently pitched pairs by dancers primarily in Spain, the Balearic Islands, and southern Italy. In Spain castanets may be used to accompany classical or folkloric dances. Typically, in the classical playing style, pairs of castanets are attached to each thumb; a simple rhythm is performed on the left-hand pair, while the higher-pitched right-hand pair plays a more complicated rhythm. In the folkloric playing style, they are attached to one or more fingers on each hand, both pairs are larger and lower-pitched than those used in the classical playing style, and rhythms are produced by flicking them with the wrists against the palms.

Orchestral castanets, which are generally used to enhance the Spanish flavour of a piece, are attached to handles and shaken or are fastened to a block of wood and played with the fingers or drumsticks. Similar instruments—often boot-shaped—were played by the ancient Greeks (krotala), Romans (crotala), and Egyptians and may have been introduced to Spain through ancient Phoenician colonization or, in their pear-shaped form, by the Moors.