Vọng cổ (Vietnamese: [vâwŋmˀ ko᷉], chữ Hán: 望古, "nostalgia") is a Vietnamese song and musical structure used primarily in the cải lương theater music and nhạc tài tử chamber music of southern Vietnam.[1] It was composed sometime between 1917 and 1919 by Cao Văn Lầu (performing name Sáu Lầu "sixth Lầu"), of Bạc Liêu Province in southern Vietnam.[2] The song achieved great popularity and eventually its structure became the basis for numerous other songs. The tune is essentially melancholy in character and is sung using Vietnamese modal inflections.[3][4][5]
The term vọng cổ is used to mean:[6]