Nicholas Zou / More than anything, it’s a compulsion. Nicholas Zou can’t pick up a violin without tweaking its sound, meticulously moving the sound post, adjusting the bridge or otherwise tinkering with the instrument to make it sing the way it ought to.

And Zou knows what he’s doing. He was six years old when he scratched out his first notes on a toy-sized violin, and his life has revolved around the instrument ever since. The violin was the reason he left China–to study music, first at the Eastman School of Music in Rochester, N.Y., where he earned his bachelor’s degree, and then at Northwestern University for his master’s degree. The violin was what brought him to a decade-long stint playing in the Honolulu Symphony, which is where he met and fell in love with his wife Keiko, also a professional violinist.

And today, the Zous are in the violin business. They own and operate CK Violins, on Ward Avenue, where they sell, rent, build and repair violins and other stringed instruments. It may seem like a natural progression for a man who has devoted the past four decades of his life to the violin, but Zou is actually a rare breed among professional musicians.

“A lot of violinmakers, they don’t know how to play,” said Zou. “And then a lot of players, they don’t know anything about how to repair or make a violin. So the combination, knowing both, gives you an advanced understanding.”

While his understanding of the violin is, to put it mildly, advanced, Zou describes most of the repair functions he performs as basic. Too many people leave their violins in hot cars, which can melt the glue that holds them together. Others mistreat their instruments so that they need revarnishing.

“The most common thing is when the kid breaks the string and we have to install a new one,” said Zou. “In less than a minute we can put on four strings, just replace them. But as soon as the string breaks, a lot of times the bridge will fall. The bridge falls and–you look inside, and you have the sound post, and because of the pressure the sound post stands but if the bridge falls, the sound post falls.”

“I started to learn how to repair violins because I was never satisfied with the sound,” said Zou. “There’s only a little spot around which you’re allowed to move the sound post, just millimeters apart. And without the sound post, it sounds crazy. It’s like a totally nasal, sick sound.”

A healthy sound, the sound that Zou seeks, is much heavier, like a perfectly cooked steak or the roasted malt of a good beer.

“My favorite tone is a darker tone,” he said with a smile. “Rich and creamy with a lot of meat to it.”

It’s different than the clean, singing tone that less-experienced musicians often gravitate toward.

“They like a very high-pitched tone, very clear,” he said. “That’s right, though, because the student needs a violin that speaks easily, like a soprano, so they can adjust their ear to the intonation. But, number one, beginner students just look for very shiny violins. It’s because they look new, like an Apple computer.”

The Zous’ customer base is made up of players of all levels–from school children to professionals, including plenty of world-class violinists.

“One of the very famous violinists, Pinchas Zukerman, he was here,” beamed Zou. “He had a very pretty, very, very expensive Guarneri violin. It was a $5 million violin.”

And while Zukerman’s violin is among the most glamorous instruments in the world, its reason for needing repair was not so pretty. Zou said that Zukerman was sweating profusely during his Hawaii performances, causing mold to grow beneath his violin’s chinrest. Zou smiles at the memory and shows off autographs from many of those who have stopped in for repairs before major performances–he has fixed Hilary Hahn’s bow and Sarah Chang’s E string in his small store. But most of the time, it’s old symphony mates who scramble to CK Violins before a show.

“A lot of last-minute repairs,” he said. “The tail gut, it will just come off, so then the strings fly all over the place, the bridge falls off and then it’s like, ‘Oh my god! Can I have a violin immediately?’ So either they come here and pick it up or I deliver it to them because even though I don’t play full-time at the symphony, we’re still part of the family.”

Zou said he misses playing–he hasn’t performed in the decade since he and Keiko resigned for financial reasons–and he is glad for the connection to his former orchestra. Most of all, though, Zou is rewarded by the sound of his work.

“Besides opera, besides the real human voice, the violin is a voice, it’s the closest to it,” he said. “The pitch, the melodies, everything. To me, playing the violin is like having a conversation. It’s like literature, just so beautiful.”