Castanets, also called clackers or palillos, are a type of percussion instrument that makes sound by itself. They are used in Spanish, Calé, Moorish, Ottoman, Greek, Italian, Mexican, Sephardic, Portuguese, Filipino, Brazilian, and Swiss music. In ancient Greece and Rome, a similar instrument called the crotalum was used.

Castanets are made of two curved pieces joined by a string on one side. They are held in the hand and used to create clicking sounds for rhythm or a fast series of clicks that sound like a rattle. Traditionally, they are made of hardwood, such as chestnut, though fibreglass is now commonly used.

When played, a musician usually uses two pairs of castanets. Each pair is held in one hand, with the string looped over the thumb and the castanets resting on the palm. The fingers are bent to support the other side. Each pair produces a slightly different sound. The lower-pitched castanets are used to mark the main beat with the fingers joined, while the higher-pitched ones are used for variations with all four fingers, including creating rattle-like sounds.

The origins of castanets are not certain. The practice of clicking sticks together to accompany dancing is very old and was done by the Greeks and Egyptians. Many sources suggest that the Phoenicians, who traded across the Mediterranean about 3,000 years ago, helped spread the instrument. Some believe castanet-like tools were also used in Ancient Egypt, made of wood, ivory, or metal. Ancient Romans found this instrument among the people of Hispania (modern-day Spain) around 200 BC. Over time, castanets became important in folk music across Spain. In more recent history, tools like bones and spoons used in Minstrel shows and jug band music are also considered similar to castanets.

During the Baroque period, castanets were often used in dances. Composers like Jean-Baptiste Lully included them in music for dances featuring Spaniards, Egyptians, Ethiopians, and others. They were also used in dances with characters like demons and nightmares. In the ballet Flore (1669), Lully wrote that "the Africans, inventors of castanet dances, entered with a more cheerful air."

Castanets are rarely used as solo instruments, but exceptions exist. For example, Leonardo Balada’s Concertino for Castanets and Orchestra: Three Anecdotes (1977) gives castanets a central role. Another example is Conciertino für Kastagnetten und Orchester by Helmut M. Timpelan, created with castanet virtuoso José de Udaeta. Other works include Toccata Festiva for Castanets by Allan Stephenson and arrangements performed by Sonia Amelio.

In the late Ottoman Empire, performers called köçeks not only danced but also played percussion instruments, including a type of castanet known as the çarpare. These were later replaced by metal cymbals called zills.

Castanets in Spain

Castanets are often used in Spanish folk music and dances, such as the Jota, a music and dance that may have started in Aragón, and the Fandango. These instruments spread across Central Spain, Castile, and southern regions of Spain. Castanets are also used by singers and dancers in the flamenco style, especially in certain types of flamenco (like Siguiriya and those influenced by Fandango), and in other dances in Andalusia, such as the Sevillanas folk dance and escuela bolera, a dance style that resembles ballet. The name "castañuelas" comes from the Spanish word "castaña," meaning chestnut, because castanets look similar to chestnuts. In Andalusia, they are often called "palillos," which means "little sticks," and this is the term used in flamenco. In some areas of southeastern Spain, like Murcia, castanets are called "postizas" and are played in a slightly different way (held over other fingers).

Castanets were used to create a Spanish feel in the opera Carmen by Georges Bizet. They also appear in the "Dance of the Seven Veils" from Richard Strauss's opera Salome and in Richard Wagner's Tannhäuser. A unique type of castanets made of metal is used in Darius Milhaud's Les Choëphores. Castanets are also found in other musical works, such as Rimsky-Korsakov's Capriccio espagnol, Ravel's Rapsodie espagnole, Francis Poulenc's Concerto for Two Pianos and Orchestra in D minor, and Karl Jenkins's Tangollen.

Spanish influence can also be seen in the music of Naples, where castanets are present. This was noted by Athanasius Kircher in his work called Tarantella Napoletana (tono hypodorico).

Mounted castanets

In orchestral or jug band music, castanets are sometimes attached to a handle or mounted on a base to create machine castanets. This makes them easier to play but changes their sound, especially for machine castanets. Players can produce a roll using any of the three ways to hold castanets. When held in the hand, they are bounced against the fingers and palm. When using sticks, they are bounced between the fingers and the player's thigh. For machine castanets, a less satisfactory roll is made by quickly switching the two castanets with the fingers.

Handle castanets

Handle castanets were created to be used in orchestral music. A pair of castanets is attached to the end of a straight wooden stick. They help create a long, continuous sound, especially when making loud sounds on the instrument.