Hat van, in essence, is a cantillation where the tunes and rhythm depend on the contents of the sung text. The tunes and rhythms may be linked together into a suite, used in relation to a mythical occurrence with hints of features from modern life. The breathing of a hat van singer comes from his or her midriff to nasal cavity, which works as a resonance box and creates an effect appropriate for religious subjects, particularly when heard in an atmosphere of incense and candles.
The words of the chanting must be clear enough so that all those attending the ceremony are able to understand. There are two kinds of hat van: hat tho and hat len dong. Hat tho is the chanting accompanying an act of worship. Hat tho is slow, serious, and dignified. Variations in the music are few and contain little contrasting pitch and stress.
Hat len dong accompanies psychic dancing claiming to respond to occult powers and expressing the will and orders of some supernatural being. It may contain many variations depending on the number of verses sung, often coming to a climax or slowing down to the tempo of a meditation. The music instrument accompanying hat van plays a very important role, in emphasizing important passages or creating contrasting effects; in any event, the music enriches the content of the chant.
The main instrument used is the dan nguyet or moon-shaped lute, accompanied by the striking of the phach (a piece of wood or bamboo), xeng (clappers), trong chau (drum) and chieng (gong) marking the rhythm. Use may also be made of the 16-stringed zither thap luc and flute sao in the recitation of certain poetry, and of the eight-sound band dan bat am in certain ceremonies. The dress worn by hat van singers, based on the cult of the "four palaces", includes a red robe for the cult of the "heavenly palace", a yellow robe for the "underground palace", a green robe for the "musical palace" and a white robe for the “aquatic palace". The style of the robe and the headgear is related to the rank of the supernatural being honoured in the act of worship. Over time, the style of the costume may vary but the rules about the colours have remained unchanged.
The art of hat van originated in the Red River Delta and dates back to the 16th century, later spreading to the whole
