Ca tru, also known as Hat a dao, was recognised by UNESCO as an Intangible Cultural Heritage in Need of Urgent Safeguarding in October 2009.

It is an ancient type of music featuring female vocalists. It is a complex form of poetry found in the north of Viet Nam using lyrics written in traditional Vietnamese poetic forms.

Ca tru groups comprise of three performers: a female singer who uses breathing techniques and vibrations to create unique sounds while playing the clappers or striking a wooden box, and two instrumentalists who produce the deep tones of a three-stringed lute and the strong sounds of a ceremonial drum.

Ca tru singing appeared in the north around the 15th century and thrived until the early 20th century. Since then, it has lost popularity to imports of modern recreational forms and cultural activities.

This kind of singing is now practised in 15 provinces and cities across Viet Nam.