Bo Ya was a qin player

Guqin

The guqin is the modern name for a plucked seven-string Chinese musical instrument of the zither family...

 from the Spring and Autumn Period or the Warring States period. He was known by his first name of "Boya", although his surname may have been Yu (俞), thus his complete name is sometimes given as Yu Boya (俞伯牙). The Lute Platform in Hanyang, Wuhan, China was where musician Yu Boya is said to have played. He is associated with the guqin pieces Gao Shan 《高山》 ("high mountains") and Liu Shui 《流水》 ("flowing water").

According to Qin Shi, Liezi

Liezi

The Liezi is a Daoist text attributed to Lie Yukou, a circa 5th century BCE Hundred Schools of Thought philosopher, but Chinese and Western scholars believe it was compiled around the 4th century CE.-Textual history:...

 said:

"Bo Ya was good at playing the qin. Zhong Ziqi was good at to listening to the qin. When Bo Ya's will was towards high mountains in his playing, Zhong Ziqi would say, 'How towering like Mount Tai

Mount Tai

Mount Tai is a mountain of historical and cultural significance located north of the city of Tai'an, in Shandong province, People's Republic of China. The tallest peak is the Jade Emperor Peak , which is commonly reported as tall, but is described by the PRC government as .Mount Tai is one of the...

!' When Bo Ya's will was towards flowing water in his playing, Zhong Ziqi would say, 'How vast are the rivers and oceans!' Whatever Bo Ya thought of Ziqi would never fail to understand. Bo Ya said, 'Amazing! Your heart and mine are the same!' When Ziqi died, Bo Ya broke the strings [of his qin] and vowed never to play [the qin] again. Thus, there was the melody of High Mountains Flowing Water."

Bo Ya's story exemplifies the Chinese ideal of friendship. The term Zhiyin (知音，literally "to know one's music") has come to describe a close and sympathetic friend.