The janggu (Korean: 장구, also transliterated as janggo or changgo) or seyogo (세요고; 細腰鼓; lit.

[2] The two heads produce sounds of different pitch and timbre, which when played together are believed to represent the harmonious joining of Um and Yang.

[3] The janggu is one of the four components of samul nori (사물놀이), alongside the buk (북), jing (징) and kkwaenggwari (꽹과리).

[4] The oldest written records about an hourglass-shaped drum may be traced to the reign of King Munjong (1047–1084) of Goryeo as a field instrument.

[2] The yogo is thought to have originated from the idakka, an Indian instrument introduced to Korea from India during Silla (57 BC–935 AD) period.

Evidence of the yogo was depicted on the mural paintings in the tomb of Jipanhyun of Goguryeo, and from the pictures at the temple Gameunsa, the Relics of Buddha, made of bronze in the second year of King Mun (682) during the Unified Silla period.

The two skin heads are lapped onto metal hoops placed over the open ends of the body and secured by rope counter-loops.

The left head (book side) named gungpyeon is covered with a thick cowhide, horsehide, or deerskin to produce deep and low tones.