The Chinese opera style was thus adopted by the Vietnamese at an early stage. Vietnamese court opera is called hat boi (hat: to sing; boi: gesture, pose), which developed into its classical form in the fourteenth century. Outwardly, it resembles Chinese opera to a great degree. As in Chinese opera, the hat boi actors sing their lines and employ dance-like gestures. The histrionic conventions were also adopted from China, but the music, despite various Chinese influences, at least partly represents indigenous tradition.
At first, Chinese classics provided material for the plots, but later librettos relating to Vietnamese history were also written, and Chinese stories and tales were adapted to local tastes and conditions. Significant librettists were Dao Duy Tu (1572–1634) and Dao Tan (1848–1908). Hat boi gradually became popular throughout the country, especially in the south. Chinese influence continued over the centuries, and hat boi closely followed the development of many Chinese opera styles in their various phases. Facial make-up, for instance, is based on eighteenth-century Chinese standards.
The troupes originally performed for the court and the nobility in palaces and private apartments, but at the beginning of the nineteenth century a permanent opera stage was built at the imperial palace in Hué. The court had extravagant tastes in opera, and official records mention that Emperor Tu Duc (1848–83) employed an opera troupe of 150 actresses at his court as well as a renowned Chinese opera star.
The emperors at the court of Hué preserved the hat boi tradition until 1945, but with the end of imperial patronage, this tradition soon degenerated, and at present most commercial performances of hat boi are said to be only distant echoes of the classical court opera.