"I was a little bit angry at that time and had no way to continue the conversation," Zhao remembered, adding he even wanted to give up if the man still ignored him.

The defendant suddenly asked Zhao whether he had listened to a song from The Shawshank Redemption, which always sailed through his mind.

"I was excited when the man talked to me and blurted out the song's name immediately, because the film is my favorite," Zhao said.

The film tells the story of a banker who spends nearly two decades in Shawshank State Prison for the murder of his wife and her lover despite his claims of innocence.

"I'm familiar with the song, because it was one selection of the opera, The Marriage of Figaro, composed by Mozart," said Zhao.

A classical music zealot, he plays many instruments, such as flute, piano and harp. He always brings disks with his laptop.

"But the song the defendant mentioned was not on my disk," said Zhao.

Instead he played another piece from the opera for the defendant who would face a long-term sentence in prison.

When the music ended, tears streamed down the defendant's face.

Later, the prosecutor arraigned another detained defendant who raped his girlfriend. That wrongdoer, in his 30s, did not feel guilty about his behavior and kept gushing about his crimes like he was talking about a drama on television, Zhao said.

"I felt he relied on ridiculous words to hide himself and I wanted him to say what he really thought before receiving his penalty," Zhao said.The defendant then started whistling The Swan, by French composer Saint-Saens.

"He was a migrant worker and knew nothing about classical music. He was imitating what his detention keeper always whistled," Zhao said.

Zhao then played the music, which made the man fall silent.

"Later he said he wished to listen to it at a concert in the future," Zhao said.

From then on, Zhao intentionally played classical music for defendants.

He often plays different pieces on his piano next to a French window at his home in the Chaoyang district of Beijing, which is decorated in an 18th-century European style.

In 2010, Zhao played Mozart's C Major Sonata - which was specially written for children - for a drug trafficker in detention who had a 4-year-old daughter. The music made the woman burst into tears.

"They (defendants) need to release themselves and the music can make it happen," Zhao explained.

"After all, punishments in prison are not the goal for wrongdoers. What they need is to find a correct way to live and rethink their crimes."

But Zhao's music therapy doesn't always work well, as some defendants have no sense of music and ignore his efforts.

"Music is not everything. It often fits those who are extremely hopeless, anxious or irate," Zhao said.

For colleagues who look down on his innovative arraignment, Zhao said he does not pay much attention to them, since they have never tried a musical arraignment.

"Zhao Peng is friendly and always has creative ideas on work," said Yang Yonghao, one of Zhao's colleagues.

"He's changed the serious or boring image that prosecutors often give to the public and made our work more interesting."

Zhao believes the melodies that move him should also bring peace for defendants, because "music is a gift that should be felt instead of being learned".

"I believe classical music will accompany my work and life forever, because no one can take the music away from me," he added.