Wiki article on this topic: Castanets, also known as clackers or palillos, are a percussion instrument , used in Spanish, Kalo, Moorish, Ottoman, Italian, Sephardic, Swiss, and Portuguese music. In ancient Greece and ancient Rome there was a similar instrument called crotalum. The instrument consists of a pair of concave shells joined on one edge by a string. They are held in the hand and used to produce clicks for rhythmic accents or a ripping or rattling sound consisting of a rapid series of clicks. They are traditionally made of hardwood , although fibreglass is becoming increasingly popular.
In practice a player usually uses two pairs of castanets. One pair is held in each hand, with the string hooked over the thumb and the castanets resting on the palm with the fingers bent over to support the other side. Each pair will make a sound of a slightly different pitch.
The origins of the instrument are not known. The practice of clicking hand-held sticks together to accompany dancing is ancient, and was practiced by both the Greeks and the Egyptians. In more modern times, the bones and spoons used in Minstrel show and jug band music can also be considered forms of the castanet.
During the baroque period, castanets were featured prominently in dances. Composers like Jean-Baptiste Lully scored them for the music of dances which included Spaniards , Egyptians , Ethiopians , and Korybantes. In addition, they are often scored for dances involving less pleasant characters such as demons and nightmares. Their association with African dances is even stated in the ballet Flore by Lully, "… les Africains inventeurs des danses de Castagnettes entrent d'un air plus gai …"
A rare occasion where the normally accompanying instrument is given concertant solo status is Leonardo Balada's Concertino for Castanets and Orchestra Three Anecdotes. The "Conciertino für Kastagnetten und Orchester" by the German composer Helmut M. Timpelan, in cooperation with the castanet virtuoso, José de Udaeta, is another solo work for the instrument. See also the tocatta festiva for castanets by Allan Stephenson. Sonia Amelio has also performed her castanet arrangements as a concert soloist.