In ancient times there was a man who played the zither very well. Once, he played a tune in front of a cow, hoping that the cow would apperciate it. The tune was melodious, but the cow showed no reaction, and just kept on eating grass, The man sighed, and went away.
This idiom is used to indicate reasoning with stubborn people or talking to the wrong audience.
古时候，有个人琴弹得很好。一次他对着牛弹了一段曲子，希望牛也能欣赏他的技巧曲子虽然很好听，但是牛却丝毫不理会，只顾埋头吃草。这个人没办法，只好摇摇头叹了口气。
“对牛弹琴”这个成语，比喻对不懂道理的人讲道理。也用来讥笑说话的人不看对象。
