Dui Niu Tan Qin (对牛弹琴) is a well-known Chinese idiom/Chengyu.
The idiom is very easy to understand, provided you know the corresponding 4 simple Chinese characters.
- 对 (duì): Face to face; opposite; opposing
- 牛 (niú): Cattle; ox
- 弹 (tán): Play; pluck
- 琴 (qín): Qin, a seven-stringed plucked instrument
- 弹琴 (tán qín): play the Qin instrument
You can join these characters to understand the idiom.
- 对牛弹琴 (duì niú tán qín): play the music in front of a cow; wasting time
Do you think cow can understand the real meaning behind the music? It’s going to be a waste of effort.
This is exactly what happened once during the Warring States Period (战国时代, 475 BC-221 BC). A musician called Gong Mingyi (公明仪) tried to pay music in front of a cow, the cow didn’t even care about the music. This was a waste of efforts by Gong Mingyi.
So, the idiom means “preach to deaf ears” or “playing music to deaf ears” or ”dealing with a wrong person/audience”, essentially “wasting time.”