There are several different types of keyboard percussion instruments. The term typically refers to the mallet percussion instruments found in western orchestras. Included in this family are the marimba, xylophone, vibraphone, and glockenspiel.
Keyboard percussion instruments are played by striking the tone bar with a mallet. The tone bar is typically made of wood or metal, and the mallet tip may be made of wood, metal, rubber, or yarn. Underneath the tone bar is a long, cylindrical tube which allows the sound to project. These are called resonator pipes.
On the vibraphone, there is also is small fan mechanism in the resonator pipes. When engaged, it produces a vibrato effect, which occurs when the sound varies in pitch, very slightly, to produce a warm, rich tone.
The glockenspiel does not have resonator pipes. It is made from metal, often played with metal mallets, and has a sound that is sharp and piercing. It can be heard throughout an entire orchestra without additional amplification.
The largest of the keyboard percussion instruments is the marimba. It is typically made of rosewood and played with soft mallets in both solo and orchestra settings. Multiple mallets are used in both hands to facilitate playing chords and complicated musical passages.
The second largest of these instruments is the xylophone, followed by the vibraphone. The xylophone is used in band and orchestra arrangements but rarely in popular music or as a solo instrument. The vibraphone is actually a very popular solo instrument, especially in jazz music. Lionel Hampton, who began performing in the 1920s, was famous for his use of the vibraphone in jazz bands.
Smallest in the family is the the glockelspiel. German for "playing the bells," it is commonly called "orchestra bells" or simply "bells". Unlike the marimba and xylophone, both the bells and the vibraphone are made of metal.
The size of the instrument is typically dictated by the number of octaves it can play. Marimbas can have up to five octaves, xylophones typically have three and a half, and vibraphones have three. The glockenspiel usually has only two, both located in a very high register.
The tone bar changes in size based on the register and pitch of the note. A marimba usually has longer and wider tone bars than the other keyboard percussion instruments, as it reaches very low notes. The glockenspiel, on the other hand, has small, short tone bars.