Music to file teeth to: Gamelan has influenced Western composers from Debussy to Glass. Composer and producer Martin Gordon travelled through Indonesia to meet and play with the masters of an ancient but evolving form

In the plane we are given small drawings of men and women. One pair, casually dressed in jeans and sandals and enthusiastically crossed out in red, are being sneered at by an official. The other couple, sombrely attired in suit and tie, knee-length hemline and sensible footwear, are being greeted by the same man with outstretched hand, and have been awarded a red tick for their efforts. I get the picture - in Indonesia, you've got to be appropriately dressed.

The music of Bali - a Hindu island afloat in a Muslim sea - was described by the American composer Colin McPhee as the 'stirring mystery of a thousand bells'. The instrument that produces this quintessentially Indonesian sound is the gamelan; it is rather like our vibes or xylophone, with bamboo or bronze keys struck by hand- held hammers. Most of the gamelans that have found their way to the West are Javanese, perhaps because the Javanese gamelan is easier to master, but the difference between the Javanese and Balinese styles is radical. If Java is the Pink Floyd of gamelan - smooth, reflective, sedate, burnished, courtly in origin - then Bali would be the Small Faces - dynamic, bright, sparkling, clangorous, popular.

The structure of gamelan is quite different from that of Western music, as is the tuning. Structurally, it sounds like dozens of interlocking circles of different lengths all moving independently, sometimes joining up, sometimes spinning off eccentrically. Musically, each instrument has its twin - each part is played by at least two instruments - and one of each pair is deliberately tuned sharp to the other, giving gamelan its idiosyncratic quality.

There are a myriad styles. Some are well known in the West - McPhee was only one of many composers influenced by gamelan, from Debussy, Satie and Benjamin Britten to Cage, Reich and Philip Glass - while others are buried deep within the island itself. The most popular form of Balinese gamelan, gong kebyar, first appeared in 1915, becoming so pervasive that other styles are now dying out. Since gamelan music is transmitted orally, as the number of older players dwindles with age, so the older styles face extinction.

I have come across tales of the gamelan jegog, built from giant bamboo trees that grow only in the west of Bali, and of the gamelan gong bheri, played by bowler-hatted musicians on Chinese-style gongs saved from a shipwreck, but such few recordings as there are of these styles are now impossible to find.

It seems the only way to experience these recondite rhythms is to track them down myself.

I have arranged a rendezvous with I Made Bandem, principal of STSI, the college of the performing arts in Denpasar, and a significant and respected figure in what is cunningly termed 'world music'. Upon arriving in Bali, the first thing I do is show my proposed wardrobe to Kadek, my 'gatekeeper' (an anthropological term for the guide who introduces you into a new society).

She is horrified: it most certainly would not do - Mr Bandem would be appalled. We go shopping.

The scent of frangipani blossom and incense lingers in the air as we reach the campus for my rendezvous. But my pleasure soon evaporates when I see that students and teachers alike are all wearing tracksuits and trainers. Mr Bandem greets me in a fluorescent green shell-suit. I eye my gatekeeper balefully, having just spent the equivalent of a week's supply of DAT tapes on 'sensible' clothing. Fridays, it appears, are now designated 'casual attire days' in Bali.

Made Bandem introduces me to Ketut Swentra, leader of Swar Agung, Bali's leading gamelan jegog. He has formed a foundation to preserve the style.

'All that the young kids really know about is gong kebyar,' he says. 'To be able to play this music, you have to understand bamboo itself - you have to grow up with it.'

At his family home in Negara, I listen to his 15-strong group. Set inside wooden frames carved into depictions of fearsome monsters, the 9ft-long jegogs rear over the heads of the players. The music is rhythmic and dense, and outrageously syncopated. In other gamelan styles, one person plays the simple polos part and another the more complicated sangsih - here each musician plays both parts simultaneously. They move into another style - jejog bumbung - which absorbed elements of Japanese music from the occupying forces during the Second World War. This music is even faster, full of dizzying twists and turns and changes of pace. It is unlike anything I've ever heard - the bass sounds like a chorus of stoned Gregorian monks after a hard night's chanting.

Next on my list is the gamelan genggong, featuring what some Balinese describe as the oldest instrument in the world, the genggong mouth-harp.

Made from a dried palm-leaf, it makes a noise rather like a musical frog - in fact the genggong traditionally accompanies the kodok (frog) dance.

Travelling by motorbike to the village of Batuan, I meet I Made Jimat, Bali's leading genggong player (genggongist?), and his group.

Sitting cross-legged in a row, the five venerable musicians hold their tiny genggongs up to their open mouths for resonance as they perform the Balinese story of the princess and the frog on these small, brightly-painted, red ovals. In Bali, music is an integral part of daily life, inseparable from religion, theatre and dance. Every village has at least one gamelan and takes fierce pride in its performances. Colin McPhee tells of seeing an entire audience leaping to its feet with outrage at a missed jegog note. As elsewhere in the developing world, the notion of playing music for a living is recent. Tourism provides a living wage for some musicians but, in the main, musicians and dancers work by day and perform at night - workers in the rice fields appear in the evenings recast as the Barong, Lord of the jungle, or the evil, fanged witch Rangda.

In Ubud, I came across kecak. It has a curiously international pedigree for such a definitively Balinese artform. The music accompanies a tale from the Hindu Ramayana. Singers and dancers perform a story about Hanoman, the monkey god, while 100 or so men play the part of his monkey army. Yet both presentation and scenario were concocted in the 1930s for a Hollywood film - the creators being the Russian-born German musician Walter Spies and an American choreographer - an ethnologist's nightmare.

Musically, it's a combination of simian chattering, vocalised gamelan and drum parts, and occasional sung melodies, and is probably based on fragments of ancient Balinese exorcism rituals. The performers surround a flaming tree, which provides the only light for their eerie performance. I set up in the shadow of the temple gate, hoping to be inconspicuous. And I am - a large Balinese musician stumbles into me and sends my DAT recorder flying.

Muttering my own obscure English ritual oaths, I retrieve it. The benign influence of Hanoman is clearly at work - my DAT machine is still functioning.

We sit in front of the temple, as a guru teaches me some of his new pieces by the traditional method of demonstration and repetition.

I play in Britain's only Balinese gamelan angklung, the SOAS- based Gamelan Kembang Kirang, and Sanding is home to a respected guru. The angklung, one of the oldest gamelans, is used to accompany cremations and tooth- filing ceremonies. The energy in the music provides a source of strength for the listener in times of distress or pain - I know, having fallen down a hole (running away from a mad dog, since you ask) and fractured my foot.

Next year is the 50th anniversary of the Republic of Indonesia and, hopefully, there'll be opportunities closer to home to sample the music of the gamelan. As for me, I'm obsessed with the ones that got away: the gong bheri had temporarily disbanded, the 24 flutes of the suling gamelan of Batuan had just lost their only regular gig, and the kendang maburung was locked in its shed and no one had the key.

Gamelan Kembang Kirang are at the Ministry of Sound, London, 27 Oct, and are available for weddings, barmitzvahs, cremations and tooth-filing ceremonies on 071-835 1620 (Photograph omitted)