He first played a fine and elegant piece of music. The cow didn't listen at all and hung its head to graze as usual. That was not because the cow hadn't hear the melody but because it couldn't appreciate the sweet music.
Later he played another piece of music which contained the buzz of mosquitoes and gadflies, also the bleat of a lonely calf. No sooner had the cow heard the music than it wagged its tail and held up its ears. Then it paced up and down leisurely and listened to the music in fascination.
─Translated from Hong Ming Ji(An Anthology of Advocating Buddhism)
【 Explanatory Notes on the Title 】
The story of this set phrase puts forward a principle that one should known the object well and have it in view before doing anything. Only in this way can he gey the desired result. But not the meaning of this set phrase has changed. It metaphorically means that explaining principle to the ignorant will certainly prove fruitless.