Lan Wangji listens to him, intently, at first not understanding what tune he is trying to play before realizing he isn't trying to play music at all. No, this is Inquiry. But he's not... doing any asking. He's playing for Lan Wangji.

He understands. Well, he thinks he understands.

When Wei Ying is done playing him the instructions, he holds his hand out as if asking for Chenqing. They don't have time to go get his guqin for him to relay a message back.