rear part of a Noh stage
In Noh theater, the area at the back of the stage where musicians (hayashi) sit.
能舞台の後座には囃子方が座る。
The musicians sit in the rear part of the Noh stage.
Compound of 後 (ato, 'back') and 座 (za, 'seat'). The reading あとざ is a rendaku form of あと + ざ.