Dạ cổ hoài lang (Vietnamese: [zâːˀ ko᷉ hwâːj laːŋ], "Night Drum Beats Cause Longing for Absent Husband") is a Vietnamese song, composed circa 1918 by songwriter Cao Văn Lầu, colloquially known as "Sáu Lầu," from Bạc Liêu.
It was a massive hit across Vietnam in 1927 as it was taken up by travelling troupes and spawned many variants, versions and imitators.
[1][2] The song Dạ cổ hoài lang marked the beginning of the iconic vọng cổ melody, which has become a subgenre on its own within the đờn ca tài tử and cải lương music that for many people Lầu's Dạ cổ hoài lang is still synonymous with vọng cổ.