Chapter 14, Part 3A - Chuang Tzu

Ch'eng of North Gate said to the Yellow Emperor, "When Your Majesty performed the Hsien-ch'ih music in the wilds around Lake Tung-t'ing, I listened, and at first I was afraid. I listened some more and felt weary, and then I listened to the end and felt confused. Overwhelmed, speechless, I couldn't get hold of myself."

"It's not surprising you felt that way," said the emperor. "I performed it through man, tuned it to Heaven, went forward with ritual principle, and established it in Great Purity. Perfect music must first respond to the needs of man, accord with the reason of Heaven, proceed by the Five Virtues, and blend with spontaneity; only then can it bring order to the four seasons and bestow a final harmony upon the ten thousand things. Then the four seasons will rise one after the other, the ten thousand things will take their turn at living.

"Now flourishing, now decaying, the civil and military strains will keep them in step; now with clear notes, now with dull ones, the yin and the yang will blend all in harmony, the sounds flowing forth like light, like hibernating insects that start to wriggle again, like the crash of thunder with which I awe the world. At the end, no tail; at the beginning, no head; now dead, now alive, now flat on the ground, now up on its feet, its constancy is unending, yet there is nothing that can be counted on. That's why you felt afraid.
~ Burton Watson translation via Terebess Asia Online ~

Go here to read the introductory post to the chapters of the Book of Chuang Tzu.