The marimba (/məˈrɪmbə/) is a percussion instrument consisting of a set of wooden bars struck with yarn or rubber mallets to produce musical tones. Resonators or pipes suspended underneath the bars amplify their sound. The bars of a chromatic marimba are arranged like the keys of a piano, with the groups of two and three accidentals raised vertically, overlapping the natural bars to aid the performer both visually and physically. This instrument is a type of idiophone, but with a more resonant and lower-pitched tessitura than the xylophone.