To actually research on, record and listen to all the styles of music in Indonesia would take the same effort as doing the same for all the mainstream genres of music. Possible? Yes. In one lifetime? Not quite. There are a large number of musicians and scholars that are still getting acquainted with all the branches of traditional music in Indonesia, as they have been for generations. Even 'diverse' feels like too small a word to have our imagination spread over the entire premise. And yet, we can't expect anything less from an archipelago nation.
The Indonesians considered music as a part of everything they do. It was in their rituals, ceremonies (of both life and death), war, along with the common modes of self-expression and to accompany dance. It will become clearer as we delve into all the traditional styles and their sub-categories, that Indonesian music is something to marvel.
Traditional Indonesian music represents some sort of uniqueness, mainly because of the varied instruments used for the purpose. While performing an orchestra, as many as 40 different musical instruments are played. The following is a brief explanation about some of the more common traditional music in Indonesia.
Gamelan (pronounced Gah-Meh-Lahn) is the biggest form of traditional music in Indonesia. It's basically a whole orchestra with an amazing variety of instruments. The base of any gamelan is deeply spiritual and directly connected to the type of instruments in use. You'll see them at any social gatherings in Indonesia. The gamelan is strictly a collective effort; no instrument shines above the others in performance, but does so in its own symbolic importance. It is the most globally spread out art form from Indonesia, with gamelan groups in America and Europe. It is believed that the gamelan was created by a Javanese king in the third century and was played in his royal court.
The people who play the instruments in a gamelan are not only supposed to be skilled at them technically, but also should be spiritually linked to them. That is the essence of a gamelan; it's not just a traditional orchestra, it's like a string of music that connects the the living world with the spiritual one. Each instrument is thus one of the many that come together to create a gamelan. They are:
The Gong Ageng, which is the largest instrument in a gamelan by both, size and importance. It is the spirit of the gamelan and cannot be excluded from one. It's the deepest sounding instrument and is supposed to be played very gently. It is more prominent in Javanese gamelan. Balinese gamelan often use the Gong Wadon, which is almost as large as the Gong Ageng but a little thinner and therefore plays at a slightly higher pitch. Others in the low (bass) pitch range are the Gong Lanang and the Gong Suwuk. There are other gongs for the middle and higher sound range that are used, which are again, different in Javanese and Balinese gamelan.
The metal instruments are even more in number, the common ones being the saron, the peking, gendèr and salunding. After that, you have the cymbals, wood instruments (gambang), drums (kendang), flutes (suling), stringed instruments (bowed - rebab and plucked - zither).
The two main types of gamelan are the core Javanese gamelan and Balinese gamelan. The former is a bit formal and uses padded mallets for its metallophone instruments. Balinese gamelan is relatively more lively and uses unpadded mallets. The difference is very subtle and takes a good deal of listening both types to get a hold of.
So you have the main categories of instrument types - gongs, metallophones, string and wood - that branch out into multiple similar instruments that differ according to geographical location. The main types are from Java and Bali, and then countless other types from all the remote parts of Indonesia. Understand this, and you'll have merely gazed upon the surface of gamelan.
The kroncong is an instrument directly related to the traditional Portuguese ukulele. The ukulele was introduced to the Indonesians by Portuguese sailors. The Indonesians then adopted the instrument and made their own variants of it. The music consists of two types of kroncong: the cak and the cuk. The cak has 4 strings, is thinner and does the chords, while the cuk is thicker, has 3 strings and does the arpeggios. The combined music is thus called kroncong. You can have a woodwind (suling) or stringed (violins) on top of the rhythm pattern to produce a more complex form of kroncong.
The angklung is commonly regarded as the most popular and one of the oldest of Indonesian instruments. In 2010, it was certified as intangible heritage by UNESCO. It's one of the most intriguing wood instruments, which relies on sustained resonance on individual tubes that have their own unique resonant frequency. The tubes are mounted on two larger bamboo tubes.
The instrument was created centuries ago by the Sundanese people. The instrument, like all Indonesian instruments, is always played as a part of a larger arrangement (although it did take time for the natives to see the angklung as a part of gamelan). The instrument and the music form has a spiritual connection to Dewi Sri, the goddess of rice and fertility. The natives would play it (and still do in some parts) to appease the goddess and get a better yield of rice.
The Balinese widely use the angklung in gamelan (called gamelan angklung), combining the instrument with metallophones and medium to high range gongs. Gamelan angklung is used in celebrations as well as rituals performed after the death of a person.
The notes in an angklung are arranged in the pentatonic scale, although you have an angklung in the diatonic scale as well.
Tembang sunda, a sung poetry and classical vocal music, originated in Cianjur (West Java) in the Dutch colonial era. In those times, it was played for entertaining the aristocrats. The instruments that are played for this traditional Indonesian music are suling (bamboo flute), rebab (violin type), and kacapi (zither). Tembang sunda is also known as cianjuran, named after its place of origin.
The instruments used in a traditional tembang sunda are few, the arrangement is almost like a modern band. It revolves around the kacapi, a pitch-oriented string instrument. The lower pitch one is called the kacapi indung, while the higher pitch one is called the kacapi rincik. The kacapi indung provides the bass-pitch tune in the background. The kacapi rincik is faster and higher. It flows within the basic structure provided by the kacapi indung.
Kacapi-suling is a variant of the tembang sunda. It includes the same patterns and sounds, but without vocals in the forefront. Instead, the arrangement is kept instrumental and the suling is used to follow the two kacapi.
Culture, religion, terrain and languages make it all the more difficult to expose their music to the world. In a way, it's good because any nation would be happy to maintain their diversity. With the technology we have today, it's become easier to discover what's left to discover, which makes it even more important for the smaller populations to protect their heritage.