Slapped pipes are activated both by the public and by the wind. They consist of a radial configuration of vertical pipes tuned to a octave five-note (pentatonic) scale. When the open ends of the pipes are slapped with beach sandals or the flat of the hand, percussive tones of the scales are produced. The resonant frequency of the pipes can also be heard by listening at the open ends. Each pipe has a different harmonic. The forerunner of this instrument is a series of hollowed out bamboo tubes found in the Solomon Islands of Micronesia. They were left in situ and turned bamboo groves into singing forests. It is also related to Chinese Sheng; musical instrument made of bamboo pipes.