Whereas western orchestras are a collection of individual players who excel in one particular instrument, in the gamelan orchestra good performers are often proficient in most of the instruments. The instruments of a gamelan are tuned to each other and not to a standard pitch.
Musicians play simultaneous variations of a melodic line, creating a shimmering, pulsating sound. The musical forms in gamelan involve the repetition of melodies and rhythms. The feeling of the ensemble is cooperative, and no one instrument dominates.
The instruments of the gamelan are divided into three classes according to their musical function: the structural instruments, the melody instruments and the elaborating instruments.
The structure and rhythm is articulated by gongs of various sizes. The fast-playing instruments, kempyang and kethuk, keep a regular beat. The larger gongs, kempul and kenong, are used to mark recurring points in each musical cycle. The largest gong, the gong ageng, represents the largest time cycle and generally indicates that that section will be repeated, or the piece will move on to a new section, or will end.
The main, or skeletal, melody, called balungan, is generally played by instruments made up of tuned metal bars. These are the saron family and the slenthem.
The panerusan,or elaborating instruments, play variations on the balungan, or melody. Panerusan instruments include the gendér, suling, rebab, bonang, and gambang. The female singer is also often included, as she sings in a similar fashion to the instrumental techniques. As these include the only wind, string, and wooden percussion instruments, their timbre sound stands out from most of the gamelan.