A Vietnamese stringed instrument in the form of a horizontal monochord (one-string) zither. It is pitched with the right hand on a vertical bar that operates like an electric guitar's whammy bar while the left hand plucks the string and controls its harmonics.

Originally, the dan bau was made of just 4 parts: a bamboo tube, a wooden rod, a coconut shell half and a silk string. The string was strung across the bamboo, tied on one end to the rod, which is perpendicularly attached to the bamboo. The coconut shell was attached to the rod, serving as a resonator.

In modern times, the bamboo has been replaced by a wooden soundboard, with hardwood as the sides and softwood as the middle. An electric guitar string has replaced the traditional silk string. While the gourd is still present, it is now generally made of wood, acting only as a decorative feature. Also, most dan bau now have modern tuning machines, so the base pitch of the string can be adjusted.

The playing technique appears relatively simple at first glance, but actually requires a great deal of precision. The 5th finger of the musician's right hand rests lightly on the string at one of 7 commonly used nodes, while the thumb and index finger pluck the string using a long plectrum. With the left hand, the player pushes the flexible rod toward the instrument with the index finger to lower the pitch of the note, or pushes it away from the instrument with the thumb to raise the pitch. This technique is used to play notes not available at a node, or to add vibrato to any note.