Hát chầu văn, or hát văn, is a traditional Vietnamese folk art which combines trance singing and dancing. Its music and poetry are combined with a variety of instruments, rhythms, pauses, and tempos. Hat chau van originated in the 16th century and spread quickly. The main musical instrument used in hat van performance is the dan nguyet or moon-shaped lute. The genre is famous for its use in rituals for deity mediumship. Chau Van serves two purposes: to help hypnotize the medium for reception of the deities and to accompany the medium's actions with appropriate music.