combo

Japanese: combo

...As a result, jazz as dance music, which had gained a great number of fans during the swing era, began to move towards appreciation music. Also, various restrictions and successive conscription orders made it difficult to maintain big bands that required many members, so bands became combos (compositions of about 3 to 8 people). Players from the Midwest and other parts of the United States gathered in clubs in Harlem, New York's black neighborhood, to hold jam sessions (groups where people randomly form groups to improvise and compare their skills) every night. ...

From [Band]

...After jazz band, the word band has been widely used in the field of popular music, regardless of the composition, such as tango band, rock band, or dance band. In jazz, a small band is sometimes called a combo and is treated in contrast to a big band. [Kiyoshi Ohama]...

*Some of the terminology explanations that mention "combo" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…そのためスウィング時代を通してファンを画期的に増していたダンス音楽としてのジャズは，鑑賞音楽への道を歩むことになった。また各種の統制と相次ぐ召集令によって，多人数のメンバーを必要とするビッグ･バンドの維持は困難となり，バンドはコンボcombo(3～8人程度の編成)化した。中西部その他，全米各地から集まったプレーヤーによって，ニューヨークの黒人街ハーレムのクラブでは毎夜ジャム･セッションjam session(任意にグループを組み，即興で演奏しあって腕を比べあう集い)が行われた。…