Dan Nhi is a sort of vertical violin with two strings, a long handle and a sound box, held in front of the player like a small cello and played with a bow. It is popular among several ethnic groups in Vietnam such as: Muong, Tay, Thai, Gie Trieng, Khmer. It is also refered to as Dan Co in southern provinces of Viet Nam. Dan Nhi comprises a tubular body made of hard wood with snake or python skin stretched over one end and a bridge. The neck of the Dan Nhi has no frets. Made of hard wood, one end of the neck goes through the body; the other end slants slightly backward. There are two pegs for tuning. The two strings, which used to be made of silk, are now of metal and are tuned in fifths: C-1 D-2; F-1 C-2; or C-1 G-1. The bow is made of bamboo or wood and fitted with horsehair. The hair goes through the space between the strings. The tones of the Dan Nhi range over two octaves, from C-1 to C-3. In drawing the bow, the player uses various techniques, including legato, vibrato, staccato; combined with his fingering of the strings he can produce trills, glissando, rapid runs, etc.
The Dan Nhi is a highly expressive instrument which plays an important solo and orchestral-role. According to archaeological documents found out in Van Phuc pagoda (Phat Tich - Thanh Son - Ha Bac), an orchestra was carved on a pedestal used as a pillar of the pagoda with musical instruments coming from India and China. The orchestra consisted of 10 instrumentalists wearing costumes like the Cham ethnic group and playing the musical instruments, one of which was similar to cello with two strings (Dan Ho), which was the former form of the current two-stringed fiddle. From such evidences, it is predicted that two-stringed fiddle Nhi entered Vietnam through the Cham ethnic group or China depending on different periods and places. (According to music history by Professor Tran Van Khe and Van Thong). Nhi takes part in orchestras, such as Nha nhac, Bat am (orchestra of eight traditional musical instruments), Tai tu band, Chau van, orchestra for Tuong stage, Cheo... The sound of the Dan Nhi is said to imitate that of a singer. It can be played in either short staccato notes or longer chords and can be played slow or fast to suit any composition.