Tu Phu religious belief is the local belief of the Viet ethnic group. This belief has many rituals and religious celebrations. Hau bong ritual is the typical one of those forms.

Hau bong is a ritual for Tu Phu saints to get into the medium. When the saint gets into the medium, the medium is the holy saint to commend and do favour to the religious people. To serve this important ritual, a kind of music called Van singing, together with an orchestra accompanying Van singing and supporting the process of getting into the medium was created. This orchestra was called Hau bong. The orchestra consists of one Moon-shaped lute Nguyet, a Two-stringed fiddle Nhi, a flute, a big drum, a small drum, one double-canh (a small gong without knob), and one castanets. Depending on each region and situation of celebrating ceremony, musical instruments can be added or diminished. Moon-shaped lute Nguyet, small drum, double-canh can not be diminished because they are the key instruments of Hau bong orchestra