Music is a rich tradition in Bali.  It is how stories are told, expressions are made, and how religion is expressed.  Most instruments are made of bronze and/or bamboo.  The main ensemble in Bali is the gamelan, which is a rough equivalent to "orchestra". 

The instruments in the traditional Balinese gamelan ensemble are:

1) the gongs : gong (the largest), kempur (middle-sized), and kemong (the smallest) 

2) the kantilans (bamboo bodies & tuning tubes with bronze keys; similar to a Western xylophone) : jegogan (largest, 5 keys), calung (second largest, 5 keys), ugal (third largest, 10 keys), and pemade (smallest, 10 keys);  these are all played with small, wooden, hammer-like mallets

3) reyong : a series of 12 kettles in a row ordered highest pitch to lowest pitch; played by 4 people; played with straight wooden stick-like mallets; the kettles look like a cooking pot with no handle and the knobbed lid fused onto the top

4) trompong : a larger version of the reyong & played by only one person

5) kendang : these are the drums; there are usually one or two kendang players in an ensemble; the kendang players are the leaders of the gamelan and give signals to the players through certain patterns as to when to move to the next section of the piece, when to change the pace of the piece, and when to change the dynamic level of a piece;  both ends of the kendang are struck to produce tones: the larger side produces a deeper tone than the smaller side; the kendang may be played with either hands or with mallets

6) cengceng : five small cymbals (about 5-6 inches in diameter) are mounted onto a wooden board; the player strikes these with two identical handheld cymbals; these are struck rhythmically & usually quickly

7) kempli : a large kettle, like those on the reyong & trompong, with a wooden base; the kempli is struck on the beat and is used for timekeeping purposes

8) suling : this is the bamboo flute; it is held vertically and has 5 or 6 tone holes

9) rebab : this is the string instrument; it is played with a bow and has two strings

Other instruments include:

tingklik : a bamboo xylophone; has either 11 or 13 keys, depending on the tingklik; one person plays it with two mallets (long skinny sticks with round rubber heads)

cak : the voice used as a instrument; there are cak gamelan ensembles (used almost exclusively for tourist attraction); the voice is used to imitate the percussive sounds of a monkey army

Balinese music is based on a gong cycle.  This means that the cycle (sentence/phrase) ends with the sounding of the largest & main gong.  Above this is (in order): jegogan, calung, ugal, & pemade.  The ugal plays the main melody of the piece.  The pemade plays the interlocking "decorative" parts.  Half of the pemade plays polos (with the beat) while the other half plays sangsih (off the beat/syncopated).  The reyong also plays a rather "decorative" part over the melody.  Throughout the piece, the kempli is keeping the beat.

All Balinese music is memorized and learned by rote.  Pieces are passed down throughout generations.  Those learning a new piece play it many times over until the piece or section has "entered them."  After a piece has entered the player, they do not forget it.  Many people begin playing gamelan instruments at very young ages.