The Modern Instrument
The marimba is a
musical instrument in the
percussion family. Keys or bars (usually made of wood) are struck with mallets to produce musical tones. The keys are arranged as those of a
piano, with the accidentals raised vertically and overlapping the natural keys to aid the performer both visually and physically.
The concert marimba is pitched an
octave lower than its cousin, the
xylophone. Both xylophone and marimba bars are usually made of
rosewood, but presently, synthetic substitutions are becoming more and more popular. Another material also being used to make marimbas is glass (see:
glass marimba). The bars of the marimba are wider and thinner than those of the xylophone, especially at the center; this change in shape causes the bars to respond a different set of overtones found in the overtone series, giving the instrument a richer tone. In particular the first overtone is two octaves above the fundamental frequency of the key, whereas a xylophone key's first overtone is an octave and a fifth above the fundamental. The result is that a xylophone will have a much brighter and shorter sound and is played with relatively hard mallet than the more mellow marimba which is typically played using comparatively softer mallets. Also whereas the xylophone's key widths are constant along its entire length, modern marimba keys are usually short (both lengthwise and widthwise) at the higher-pitched end and gradually "graduate" into the bottom octaves. This ensures that larger marimbas, such as 5-octaves, have enough material to generate low notes and overtones.
Resonators 
The key to the marimba's rich sound is its
resonators. These are metal tubes below each bar, the length varying according to the pitch of the note. Vibrations from the bars resonate as they pass through the tubes, which act not unlike the main body of a cello or guitar by amplifying the sound. In exceptionally large instruments (typically above 4 1/2 octaves) the length of tubing required for the
bass notes exceeds the height of the instrument and the resonators are bent at the bottom.
ApplicationModern marimba uses include solo performances, percussion ensembles, marimba concertos, jazz ensembles, marching band (front ensembles), and wind ensemble or orchestra compositions. Contemporary composers have utilized the unique sound of the marimba more and more in recent years, and it is common to find them in most new music for wind ensemble, although less so for orchestra.
The Folk Instrument
Folk marimba with gourds, Highland
Guatemala 
The term marimba is also used to refer to various traditional folk instruments, the precursors of which may have developed independently in West
Africa and in
Pre-Columbian Mesoamerica. The tradition of the gourd-resonated and equal-ratio heptatonic-tuned Timbila of Mozambique is particularly well-developed, and is typically played in large ensembles in coordination with a choreographed dancing performance, such as those depicting a historical dramatization. Traditional marimba bands are specially popular in
Guatemala, where they are the national symbol of culture, but are also found in
Costa Rica and parts of the highlands of southern
Mexico, as well as among
Afro-Ecuadorians;
gyil duets are the traditional music of
Dagara funerals in
Ghana.
ResonatorsIn the most traditional versions, various sizes of natural
gourds are attached below the keys to act as resonators; in more sophisticated versions carved wooden resonators are substituted, allowing for more precise tuning of pitch. In Central America, a hole is often carved into the bottom of each resonator and then covered with sheep skin to add a characteristic "buzzing" or "rattling" sound.
In more contemporary style marimbas wood is substitituted with PVC tubing. The holes in the bottoms of the tubes are covered with a thin layer of paper to produce the buzzing noise.
ZimbabweanZimbabwean marimba based upon
Shona music has also become popular in the West, which adopted the original use of these instruments to play transcriptions of
mbira dzavadzimu (as well as nyunga nyunga and matepe) music. The first of these transcriptions had orignally been used for music education in Zimbabwe. These Zimbabwean-style instruments are often made with a single row of keys (without the chromatic "black" notes on a second row) along a C major scale, which allows them to be played with a 'western-tuned' mbira (G nyamaropa). Frequently instruments are fashioned with the addition of an F# key placed inline between the F and G keys, which allows the playing of songs in G major, although the correspondence between mbira tunings and western keys is a much more complex issue. Other variations in tuning exist, and some musicians prefer the omission of the F# key. In the United States, there are Zimbabwean marimba bands in particularly high concentration in Colorado and the Pacific Northwest, but bands exist from the East Coast through California and even to
Hawaii. The main event for this community is
ZimFest, the annual Zimbabwean Music Festival. The bands are composed of instruments from high sopranos, through to lower soprano, tenor, baritone, and bass. Resonators are usually made with holes covered by thin cellophane to achieve the characteristic buzzing sound. As of 2006, the repertoires of United-States bands tends to have a great overlap, due to the common source of the Zimbabwean musician
Dumisani Maraire, who was one of the few key people who first brought Zimbawean music to the West, coming to the University of Washington in 1968. Some notable past and present US Zimbabwean marimba bands include
Boka,
Hokoyo,
Kutandara, Musango, Ukama, and
Anzanga.
Mallets 
The mallet handle is commonly made of wood, but may also be metal or carbon fiber. The diameter of the handle can range from .25 - 1 inch. The head of the mallet can be rubber, or wood wrapped in yarn. The diameter of the mallet
head can be 1 - 3 inches. The handle diameter and head size increase proportionally to the size of instrument's keys. Handle diameter can also be influenced by mallet technique in the sense that multiple mallets in the same hand will require a smaller diameter.
Mallet Technique
Modern marimba music calls for simultaneous use of between two and eight mallets, granting the performer greater virtuosity and range. Multiple mallets are held in the same hand using any of a number of techniques or grips. For use of two mallets is each hand, the most common grips are the
Burton grip (made popular by
Gary Burton), the traditional grip (or "cross grip"), the Musser grip, and the
Stevens grip (made popular by
Leigh Howard Stevens). Each grip is perceived to have its own benefits and drawbacks. Choice of grip varies by region (Stevens grip and Burton grip are more popular in the
United States, while traditional grip is more popular in
Japan), by instrument (Burton grip is less likely to be used on marimba than on
vibraphone) and by the taste of the individual performer.
Here is a link to another great marimba site
Greg Latta's Marimba Page
