The people in charge of performing music in the Tứ Phủ belief are called cung văn. A person practicing the cung văn profession has to train for a long time, from five years to seven years. This person has to be excellent in writing Hán-Nôm words and organizing a worship ceremony and hát văn so that he/she can take care of a temple. The cung văn profession is transferred only to family members. Hát văn music is usually performed by two cung văn, including one person playing the nguyệt (moon-shaped lute) and the other playing percussion instruments. One of them or both can sing. In a big rite, the number of performers in a band can be four or five with the participation of the tranh (16-chord zither), the nhị (Vietnamese two-string fiddle), or flutes. The nguyệt originates from the yeuqin instrument of China. However, comparing to the yeuqin instrument, the nguyệt has a longer neck with eight to eleven frets. A neck with ten frets is the most popular. Two strings of this instrument used to be made of silk but now are made of nylon. The small string is called dây tiếu, and the bigger one is called dây đài. The nguyệt is usually tuned to dây bằng (the fifth interval) and dây lệch (the fourth interval). It is seldom tuned to dây tố lan (the minor seventh interval) and to dây song thanh (an octave).