The main instrumental forces of the gong kebyar orchestra are metallophones. There are typically four pemades and four kantillan - collectively known as the gangsa - which play the most complex parts. There are either one or two ugal, which play an ornamented version of the main melody - the pokok - of the piece. Lower pitched metallophones - jublag, jegogan, and sometimes penyacah - play increasingly abstracted versions of that melody. All of these instruments metallophones are played in pairs, with each pair tuned slightly apart. This produces a beating effect (ombak) and creates an overall shimmering, pulsating quality.
Other instruments in the orchestra include the reong - a set of twelve bossed bronze "pots"; the ketuk - another "pot" similar in appearance but larger than an individual reong; the gongs, which mark the essential structural points in the music; kendang - the drums, which control the tempo of ensemble and reinforce the meter; ceng-ceng - small, mounted hand cymbals which play fast, intricate parts, usually along with the reong; suling - flutes, which play somewhat improvised ornaments on the pokok; and, occasionally, the rebab - a spike fiddle, which plays along with the suling.
Gong kebyar music is based on a five-tone scale called pelog selisir (tones 1, 2, 3, 5, and 6 of the 7-tone pelog scale), and is characterized by brilliant sounds, syncopations, sudden and gradual changes in sound colour, dynamics, tempo and articulation, and complex, complementary interlocking melodic and rhythmic patterns called kotekan.
The music is divided into 4 beat groups called Keteg, this whole rhythmic cycle is called the gongan. The gongs divide gongan into sections, gong ageng, the largest gong, marks the end of gongen, the smaller gongs mark the 4th or 8th keteg and the smallest gongs outline the pulse.
The kebyar style developed out of older ensembles and first emerged in the early 20th century.