The xylophone consists of a row of tuned wooden sound bars mounted on a frame. The attack is usually made with two mallets, usually wooden mallets, about 30cm long. The sound of the xylophone is short and percussive. The xylophone is available in three sizes: soprano - high notes, tenor / alto - medium notes, large bass - low notes. The bars are also available individually with their own sound box made of wood or plastic and are called "sounding bars".