“Đăng đàn cung” first appeared during the reign of emporer Gia Long, who asked Jean-Baptiste Chaigneau (a French bureaucat in the Vietnamese court who took the Vietnamese name Nguyễn Văn Thắng) upon his accession in 1802 to compose an anthem. The resulting piece was used during important events in the court and to honour the monarch. It appears to have remained wordless until the reign of Bảo Đại, who took the throne in 1932. It was made the official anthem of the Empire of Vietnam (a short-lived Japanese puppet state set up in March, 1945) and was disestablished upon the surrender of Japan in August, 1945 and the seizing of power by the Vietminh, which ended the Vietnamese monarchy.
Special thanks to: Arben Saavedra for informing me of this anthem.