with a stick. Instruments with three or more strings may be plucked with the thumbnails. These may also be played with a combination of thumbnail and stick, the player moving back and forth between plucked and hammered notes. Ensembles, gumbeng and chelempung The traditional ensemble music of Indonesia centers around gong and gong-chime based ensembles, called gamelans. The music was imitated with other instruments, including bamboo-based ensembles. The Gumbeng ensemble includes a polychordal bamboo-tube zither with bamboo strings to play melody, a second bamboo-tube zither set up as a parallel-string instrument (strings connected together and sounding together and functioning as "kempul") another string making "kenong beats", a bamboo-tube (not a zither) functioning as "kedang" by beating open ends of the tube with the palms of the hands, a bamboo-tube instrument blown as a gong. The chelempung ensemble or celempung, found today on Java and in places under Javanese influence (including Sumatra), consists normally of rows of "bonang" kettle bells, in rows of 3 or 5 bells. However, instruments may substitute for the kettle bells, including a single celempung metal-stringed zither or a chelempung orchestra consisting of idiochord-bamboo tube zithers. In this last ensemble, instruments may be named for their function in the orchestra: the kendang awi (bamboo kendang) replaces the kendang drum; the ketuk awi (bamboo ketuk) replaces the ketuk gong-chime part. Another instrument used with this ensemble is the celempung renteng, which refers to a row (reteng) of parallel-string tube zithers (celempung). This row has tube zithers of different sizes, each playing a different note, like tone-bars on a xylophone. Strings tuned to higher notes imitate the gamelan chimes, and lower note strings imitate gongs. Another zither used in the chelempung ensemble is a three-string celempung indung. The instrument is polychordal, with strings played individually to make different notes. Bridges can be placed under the strings in the center of two of the strings, allowing even more notes, on either side of the bridge. The lowest note string has been designed to make a "sustained boom" through the use of a flap, over a hole in the bamboo tubing; the flap vibrates with the string and "this sound/energy is transmitted through the length of the tube through the small hole." The kendang drum is imitated by hitting the open end of the tube with the palm of the musician's hand. A player can also influence the pitch of the