Castanets
When they are played in an orchestra they are often attached to a stand.  The technique of playing is therefore different.  They can be tapped by the fingers and palm of the hand.  They are often used in music which is supposed to sound Spanish.  In ballet and opera they are used to accompany Spanish dances.  Carmen, the character in Bizet's opera Carmen, sings a song and accompanies herself on the castanets.  Usually the opera singer does not have the skill to play them, so the castanets are played by a percussion player in the orchestra while Carmen pretends to be playing them.