对 duì = prep. to, at, concerning to 弹 tán = vb. to play (an instrument)
牛 niú = n. cow 琴 qín = n. zither, lute (a kind of musical instrument)
This idiom literally means play the zither/lute to the cow. It means ‘to address the wrong audience’ or ‘to talk over somebody’s head.’
The story goes…..Gong Mingyi was a fantastic lute player who lived in the Warring States Period. One day he saw a cow eating grass and, thinking it a good idea, decided to play beautiful music for the cow. However, the cow continued eating grass like nothing was going on. The people who were watching this spectacle said, “It is not because your song sounds bad, only that you have sought the wrong audience.”
Now people use this saying to mean that the audience cannot follow the speaker’s meaning.
Trans: She read them Shakespeare, but it was casting pearls before swine.