During the Spring and Autumn Period (770-476 B.C.), there lived a renowned music master named Yu Boya. He possessed superb skill in playing the guqin (a seven-stringed zither), yet felt he could not fully express the profound impressions of the world through his music.
His teacher, understanding his frustration, took him by boat to Penglai Island in the East China Sea, a fabled abode of immortals. There, Boya immersed himself in nature: the roaring waves leaping skyward, sea birds circling with pleasant cries, and lush green forests. A harmonious and intriguing feeling welled up within him, as if he were hearing the music of nature itself. He took up his instrument and played, freely incorporating the beauty around him into his music, reaching a realm of artistry he had never before experienced. "You have mastered the art," his teacher declared.
One evening, on the 15th day of the 8th lunar month, Boya was boating under a bright moon and a cool breeze. Myriad thoughts filled his mind, and he began to play. His melodious music was so captivating that a man on the shore shouted "Bravo!"
Boya emerged to find a woodcutter, Zhong Ziqi, standing on the bank. Recognizing a kindred spirit who truly understood his art, Boya eagerly invited him aboard. When Boya played a piece eulogizing high mountains, Zhong said, "Wonderful! The melody is as magnificent and dignified as Mount Tai reaching for the sky!" When Boya played a piece depicting turbulent waves, Zhong exclaimed, "Wonderful! It is as vast and mighty as a great river!"
Overjoyed, Boya cried, "Bosom friend! You are truly my bosom friend!" From that day, they became the closest of companions.
This story from The Works of Liezi gave rise to the idiom "high mountains and flowing waters" (gāo shān liú shuǐ). It refers to a deep, understanding friendship between kindred spirits, or to describe supremely beautiful and resonant music.