The instrument existed as far back as 3,000 years ago. By virtue of its construction, this is the only unique Chinese musical instrument in the Chinese orchestra capable of playing up to six notes simultaneously. It is therefore commonly called as the "Chinese mouth organ" by western people. Sheng is also the first musical instrument in the world utilizing a "coupled acoustical system," between an air column and a free reed. Sheng consists of 13-17 bamboo pipes with different lengths that are mounted together onto a base. The base is traditionally a gourd-shaped, wooden wind-chest. Each bamboo pipe has a free reed made of brass. Music is produced by blowing and sucking the air through a metal tube connected to the base. From the base the air then rushes through the other pipes. A player determines the notes to play by allowing the air to rush through selected pipes while pressing on selected keys near the base. By covering two or more holes on various pipes, chords are possible, being a typical technique used in most regional orchestras of China. The sheng is used as both a solo and accompaniment instrument.