concert pitch
Refers to the standard tuning pitch used by orchestras and ensembles, typically A=440 Hz or similar reference.
オーケストラは合奏調に合わせてチューニングする。
The orchestra tunes to concert pitch.
Compound of 合奏 (ensemble, concert) and 調 (tuning, pitch). The exact historical derivation is uncertain, but the term is used in modern musical contexts.