Ca trù (歌籌) "Tally Card Songs" also known as hát ả đào or hát nói, is an ancient genre of chamber music featuring female vocalists, with origins in northern Vietnam. For much of its history, it was associated with a geisha-like form of entertainment, which combined entertaining wealthy people as well as performing religious songs for the royal court.
Ca trù is inscribed on the list of Intangible Cultural Heritage in need of Urgent Safeguarding in 2009.
There are different myths and theories related to ca trù's conception. One story states that a woman named Ả Đào created the genre, having charmed the enemy with her voice (thus explaining one of the genre's alternate names: Hát ả Đào). Another theory points to a woman named Đào Thị, a talented musician who was beloved by the Lý Dynasty imperial court. This theory also claims that ever since the time of Đào Thị, in admiration of her, women who held a profession as singers (such as ca trù singers) were referred to as Đào nương ("nương" here refers roughly to "maiden" or "lady"). The latter is true although this term is no longer widely used in modern Vietnam.
What is known for sure is that ca trù started off like many of Vietnam's arts as being a form of entertainment for the royal court. Officially ca tru count the age of their profession since The Later Ly dynasty (Vietnamese: Nhà Hậu Lý, 1010—1225), at that time musicians called Vietnamese: hát khuôn performed only on religious court ceremonies. It was only later on that it branched out into being performed at small inns. Indeed, it was mainly scholars and other members of the elite who enjoyed the genre, which was somewhat inaccessible to the masses (who enjoyed the Hát chèo opera genre much more).
In the 15th century ca tru spread through Northern Vietnam. The artists might be called to celebrate a son's birth, or to celebrate the signing of a contract. Ca tru were outside of the caste system, so they could entertain the most noble clients.
In the 19th century, after Vietnam was colonized by French, Ca Tru had significant changes. Beside the noble clients, who have very high education, there was a new class of Vietnam's society who worked for the French government, they were rich but most of them didn't have good education. At that time, Vietnamese people looked down to the people who cooperated with French, that thought made those people came to Ca Tru because it made them feel they're equal with noble people. Ca Tru required a very high education from the clients which the new class didn't have. Couldn't enjoy the art of Ca Tru, those people look for another thing, sex. Ca Tru slowly became a type of prostitution.