Wikipedia
Janggu
The janggu (or janggo; also spelled changgo) or sometimes called seyogo (slim waist drum) is the most widely used drum used in the traditional music of Korea. It is available in most kinds, and consists of an hourglass-shaped body with two heads made from animal skin. The two heads produce sounds of different pitch and timbre, which when played together are believed to represent the harmony of man and woman.