The dan bau (đàn bầu) is a unique Vietnamese national instrument, a monochord — that is, a zither with only a single string. Despite such extreme simplicity of construction, it is capable of reproducing an extraordinarily expressive, “singing” melody across a wide range.
The secret lies in the manner of playing: the musician plucks the string while touching it at its division points to draw out pure harmonics (overtones). With the other hand they flexibly bend a vertical rod attached to the string, changing its tension — and thereby raise or lower the pitch, creating smooth glissandos and a characteristic “vocal” vibrato. The voice of the dan bau so resembles human singing that a Vietnamese proverb warns young women not to listen to it alone. It is one of the most poetic and moving instruments in the world.
