《礼记·乐记》
乐师只能辨别声律和诗句，所以只能在堂下面朝北弹琴。宗祝只不过了解宗庙的具体仪式，所以只能站在尸的后面。商祝只懂得丧葬的礼仪，所以只能站在主人后面。
乐师辨乎声诗，故北面而弦；宗祝辨乎宗庙之礼，故后尸；商祝辨乎丧礼，故后主人。
The musician can only distinguish sound rhythms and poetry, so he can only play the piano sitting facing north in the hall. The Zongzhu only knows the concrete ceremony of the ancestral temple, so he can only stand behind the corpse. The Shangzhu only understands the etiquette of funerals, so he can only stand behind the host.