Liu Younian instructs his apprentice doing the tuning works in a workshop of Wuhan Mechanical Technology Institute Co Ltd in Wuhan, capital of Central China's Hubei province, on December 1, 2016. [Photo by Zhu Lingqing/chinadaily.com.cn]

A smart music sense of hearing is required in the tuning work. People in the industry praise Liu's ears as "golden ears" because he even can tell a one-twentieth difference between two tunes.

Reaching retirement, Liu no longer has the physical energy to work at the frontline. "The tuning work requires you to turn over the chime bell that can weigh 300 to 400 jin (150 to 200 kilograms) over and over again. Now I am unable to do that, so I give others instructions."

But he has also realized that experience should not only rely on oral teaching. "It needs a standard."

After participating in developing China's first national standard of bronze percussion instruments in 2010, he is now working on the research of the principle and theory behind bianzhong tuning.

Suffering from loneliness is inevitable in this work, Liu said. "Loneliness chases you every time when you have to deal with a new round of research and development or the cool market."