The k'ni or Vietnamese mouth violin is a fiddle-like instrument used by the Jarai people in Vietnam. The term is the common word for fiddle in the Jarai language. It is a bowed chordophone which uses the musician's mouth as a resonator which enables the instrument to imitate certain qualities found in vocal music.
The instrument does not have a direct equivalent among traditional Vietnamese musical instruments.
The body of k'ni is made from a bamboo tube of approximately 3 cm diameter and 66 cm long. A tuning peg is found at the upper part of the body, while at the other end of body, there are wooden pins for attaching the strings. The steel strings are attached to tuning pegs and go straight to the attachment pins. One end of the sympathetic string is closely tied to the main string near the hanging pins, while its other end is fixed after being put through the membrane which is either made of pangolin's scab or flattened buffalo horn. The bow is a hornless bamboo slab of 40 or 45 cm length and tapered at one end.
When playing, instrumentalist holds the membrane in their mouth, and stretches the sympathetic string to an appropriate length, and plays the instrument with bow. The bow is prepared with resin. The sounds of the metal string impact on the sympathetic string causing the membrane to vibrate. The musicians mouth becomes the instrument's resonator.
Folk artists usually use pentatonic scales. One of pentatonic scales of Giarai is Do1 - Re1 - Fa#1 - Sol1 - La1.