The marimba is a percussion instrument consisting of wooden bars struck with mallets. It evolved from West African instruments like the balafon and was further developed in Central America. What distinguishes the marimba from the xylophone is its range (it is lower and larger) and its use of resonators. Modern marimbas have metal tubes (resonators) hanging beneath each bar, which are tuned to the same frequency as the bar to amplify the sound and provide a rich, mellow tone. In traditional Guatemalan marimbas, the resonators are gourds with a thin membrane that creates a 'buzzing' sound. The marimba is the national instrument of Guatemala. In the 20th century, it became a standard orchestral instrument, used for its unique 'woody' and resonant timbre. Virtuoso players often use four or even six mallets simultaneously to play complex chords and melodies.