Kacapi is a zither-like Sundanese musical instrument played as the main accompanying instrument in the Tembang Sunda or Mamaos Cianjuran, kacapi suling (tembang Sunda without vocal accompaniment) genre (called kecapi seruling in Indonesian), pantun stories recitation or an additional instrument in Gamelan Degung performance.
Word kacapi in Sundanese also refers to santol tree, from which initially the wood is believed to be used for building the zither instrument.
According to its form or physical appearance, there are two kinds of kacapis:
- Kacapi Parahu (=Boat Kacapi) or Kacapi Gelung ; and
- Kacapi Siter
The Kacapi Parahu is a resonance box with an uncovered underside to allow the sound out. The sides of this kind of kacapi are tapered inward from top to bottom, which gives the instrument a boat-like shape. In ancient times, it was made directly from solid wood by perforating it.
The Kacapi siter is a plan-parallel resonance box. Similar to the kacapi parahu, its hole is located at the bottom. The upper and bottom sides of it form a trapezium-like shape.
Nowadays, the resonance box of kacapi is made by glueing six wood-plates side by side.
The kacapi is traditionally played by sitting cross-legged on the floor. Thus the strings are about 25 cm above the floor. Nowadays the kacapi is sometimes placed on a wooden frame, so that the player can sit on a chair. If the kacapi indung is played while sitting on the floor, usually a pillow or some other small object is placed under its left hand side, as seen from the player, so that the sound can freely escape through the resonance hole in the bottom of the soundbox. Some kecapi are fitted with small feet, so that it is not necessary to lift them in this way. 
According to its functions in a musical accompaniment, the kacapi is played as:
- Kacapi Indung (=mother kacapi); and
- Kacapi Anak (=child kacapi) or Kacapi Rincik
The Kacapi indung leads the accompaniment by providing intros, bridges, and interludes, as well as determining the tempo. For this purpose, a large kacapi with 18 or 20 strings is used.
The Kacapi rincik enriches the accompaniment by filling in inter-note spaces with higher frequencies, especially in fixed metered songs as in the kacapi suling or Sekar Panambih. For this purpose, a smaller kacapi with ~15 strings is used.
Tuning and Notation 
Kacapi uses degung notation. It is a subset of the pelog heptachordal system. See the following table.
|Sundanese pelog degung||Javanese pelog|
Physical dimensions 
Kacapi and recitation of pantun stories 
It is not certain how long the kacapi has been used to accompany the recitation of pantun stories. In the Sundanese dictionary published by the Lembaga Basa & Sastra Sunda (1976) the primary meaning of the word pantun is given as kacapi. This may be an indication that the relation between the kacapi and the recitation of pantun stories is an old one. Eringa (1949:3) points to the proverb "kawas pantun teu jeung kacapi", 'like a pantun(-singer) without a kacapi', used of someone who likes to give other people advice but who does not himself practise what he preaches. This proverb, according to Eringa, indicates that the kacapi is the Standard instrument for accompanying a pantun recitation. The Baduy Sundanese of Banten Province still make exclusive use of the kacapi to accompany their pantun stories.
- Wim van Zanten, Sundanese Music in the Cianjuran Style, Foris Publications, USA, 1989