A marimba is an idiophone, a percussion instrument that produces sound by means of vibrations that travel through the entire body of the instrument. The idiophone family also includes triangles and cymbals, all instruments that form part of the percussion section of an orchestra.
One subset of the idiophone family is the group of instruments played with mallets, and the marimba belongs to this group. In fact, it is the largest mallet instrument in a group that includes the vibraphone, the xylophone, the chimes or tubular bells, the glockenspiel, the steel drums, and the crotales or antique cymbals. While historically, a variety of struck and plucked instruments from Africa and Latin America have been given this name, today the term is mainly used for the modern orchestral instrument.
Like the xylophone, the orchestral marimba is a set of wooden bars, often rosewood, mounted on a stand, with each bar having its own resonator. This distinguishes it from the other mallet instruments that have bars made of metal. It is also distinguished by its resonant, mellow tone, which contrasts with the xylophone’s sound, which has little sustain and can be both brittle-sounding and piercing. The first orchestral marimbas were manufactured in the United States in 1910.
A standard "concert marimba" has a 4 1/3 octave range, while solo instruments are 5 octaves, and it is a non-transposing instrument, usually scored on the grand staff. The lowest pitches are customarily placed to the player's left. The instrument is traditionally played with a variety of mallets, but the hardest mallets are avoided so as not to risk cracking the bars.
An instrument called the xylorimba, or sometimes the xylo-marimba or marimba-xylophone, is a type of xylophone with a range that extends down into that of the marimba. Alban Berg and Olivier Messiaen wrote for xylorimba, but the parts are played on a xylophone. Pierre Boulez wrote for xylorimba in several pieces; in once case, the part is played on a xylophone, in the other, the parts are played on a combination of xylophones and marimbas. Composers for the instrument have included Percy Grainger, Darius Milhaud, Carl Orff, and Igor Stravinsky, who reportedly called for a marimba-xylophone but meant a marimba.