Generally speaking, a metallophone is any musical instrument consisting of tuned metal bars which are struck to make sound, usually with a hand-held beater.
Metallophones have been used in music for hundreds of years. There are several different types used in Balinese and Javanesenese gamelan ensembles, including the gendér and saron. These instruments have a single row of bars, and are often tuned to a pentatonic scale. The glockenspiel and vibraphone are also metallophones - these have two rows of bars and are tuned to the chromatic scale.
In music of the 20th century and beyond, the word metallophone is sometimes applied specifically to a single row of metal bars suspended over a resonator box and tuned to the diatonic scale. Such instruments are often used in schools, and Carl Orff used them in several of his pieces, including his pedagogical Schulwerk.
