Vibraphone

It was invented in the U.S. toward the beginning of the 1900's
and was popularized by the great jazz musicians Lionel Hampton
(with clarinetist Benny Goodman) and Milt Jackson of the
Modern Jazz Quartet. Some other notable vibraphonists are
Gary Burton (who popularized the use of playing with four mallets),
Cal Tjader (known for playing Latin music), and Bobby Hutcherson.

The bars of the instrument are struck by mallets of varying hardnesses.
The vibraphone looks similar to a xylophone and a marimba.
The difference is that the bars of both the xylophone and marimba are
made of wood. In general terms, the xylophone is a soprano or high
register marimba (the difference being in the tuning and timbre).
The bars of a vibraphone are made of metal. The vibraphone also has
a sustain pedal like a piano that when depressed allows the notes
to ring until the pedal is lifted again. The vibraphone originally
got its name because it has a motor that turns metal discs,
called pulsators, located under the bars at the openings of the
resonators or tubes. The rotation of the pulsators gives a "vibrato"
(more accurately tremolo) sound to the instrument. Without this motor
the vibraphone could just as easily be called a metalophone because
of it's metal bars.