The call to Hans Nebel came after hours. In tears, a musician was seeking help. The unthinkable had happened. His Stradivarius violin—one of only 600 of the Italian masterpieces still in existence—had fallen and been damaged.

Not long after, the musician appeared at Nebel’s workshop in suburban New Jersey with the wounded $3 million instrument. Nebel greeted both the musician and the violin as old friends. One of the nation’s preeminent violin restorers, Nebel had worked on Strads for decades.

“Here’s a violin that’s survived centuries and every world war, and now it’s damaged,” Nebel says, recalling the moment. “This is very upsetting to the musician; this is his baby.”

For more than 45 years, the owners of some of the world’s best violins have brought their “babies” to Hans Nebel. His clients include players from many of the premier orchestras in the world. The German-born Nebel greets them punctually with a broad, cherubic smile and impish blue eyes that exude genuine love for the art and craft of violin restoration.

“I know of nobody better,” says Bill Gailes, who studied under Nebel and now owns a violin shop in Maryland.

Most clients simply want Nebel to give their instruments a tune-up—clean, polish, and readjust the bridge. For major reconstruction work, violin owners must wait more than four years.

Once in a while, a valuable violin suffers serious damage requiring immediate attention. For the Strad, Nebel made time. He repaired the damage, touched up the scratches, and had it back in its owner’s hands in three months.

While Nebel certainly knows how to make violins, he now only mends them. His mission is unequivocal: to repair and rejuvenate the work of the great violin builders of the past.

“I find it much more challenging to take a Strad that has been damaged—for example, one that has had a corner knocked off,” Nebel says. “I have to find wood to match the piece that has been knocked out, reshape it in the style of Stradivarius, then put into that area 300 years of wear and tear, and finally retouch it to where the untrained eye cannot see the difference.”

A few miles from the George Washington Bridge, in the quiet New Jersey suburb of Harrington Park, Nebel works out of a house he designed himself to ensure that it was properly equipped for violin repair work. For example, the house features security shutters that open mechanically, and in his ground-floor workspace, Nebel installed a carefully controlled heating system and monitors to ensure against extremes in humidity, a hazard to the delicate wooden architecture of violins.

Most impressively, the ground floor also has a walk-in vault with 12-inch-thick concrete walls and a steel door capable of withstanding fire for four hours. The walls of the vault are lined with cubbyholes filled with violins that are either waiting for repairs or are owned by Nebel. The house could burn down, but the bunker—and the violins inside—would likely survive.

Nebel placed his workshop on the north side, where the indirect light is best for detail work. On one wall, facing the window, is a well-worn but thoroughly clean butcher-block workbench. A quart-size electric gluepot stands ready. Racks of maple-handled chisels and knives—many of them made by Nebel—hang alongside the workbench, as do several handmade, dagger-shaped rasps that he uses for sanding. Behind the bench, a clamp holds the top of a violin in the process of being re-glued.

Nebel typically works on violins that have been nicked or scratched. Repairing a scratch in a valuable violin can take weeks, as Nebel carefully fills the scratch with several applications of varnish, and uses natural pigments to match the original shade as closely as possible. Nebel will not attempt the varnishing unless the weather conditions are right. “If it’s a very damp day and you’re picking up a certain amount of moisture, the color will simply not flow appropriately,” he says.

Bill Gailes marvels at Nebel’s ability to repair scratches without leaving any evidence. “When Hans does it, you can’t find it. He is that good.”

Over years of heavy playing, a violin’s arching tends to become misshapen, even by a millimeter or two; Nebel can usually return the instrument to its intended shape using braces and molds. However, he can spend months on such a restoration as he makes small, gradual corrections. “I’m from the old school; I don’t do that all at once,” he says.

Such services do not come cheaply. An annual tune-up, which he recommends to his clients, can cost close to $1,000; major restorations can take a year or more and may cost $50,000.

Nebel’s list of clients includes musicians and collectors—lawyers and doctors among them. “This may sound snobbish, but most musicians in major orchestras may not own the best instruments,” Nebel says. “They can’t afford them.”

Many of Nebel’s clients have been bringing their instruments to him for years, even decades. John Merrill, a violinist with the Baltimore Symphony Orchestra, has entrusted his 229-year-old Ferdinando Gagliano violin to Nebel since the early 1970s.

During his first meeting with Nebel, Merrill was taken by the seriousness with which Nebel discussed a structural problem with Merrill’s violin. Nebel repaired it and loaned Merrill a violin his father had made. Ever since, Merrill has made the four-hour drive to Nebel’s house at least once a year for a tune-up.

“The attention to detail and precision and care with which he does everything— I respect that,” Merrill says.

In Nebel’s hometown of Mittenwald, Germany, many young people go into the violin business. The small picturesque town in the Bavarian Alps has been home to highly regarded violinmakers and restorers since the 17th century, and a violinmaking school there has been turning out luthiers for more than 140 years.

Like many others in the town, Nebel’s grandfather and great-grandfather learned how to make violins, but that was a wintertime sideline to their primary job of potato farming. Nebel’s father took the next step by attending Mittenwald’s acclaimed violin school and working for several years in America before returning home. His son, born in 1939, started playing the violin at age seven but was more interested in his father’s woodworking tools. “While other kids were out playing soccer, I was inside, sitting on my duff, dulling my father’s tools,” Nebel recalls.

His father tried to steer him away from violins. “The last thing Germany needed was another violinmaker,” Nebel says. “My father wanted me to be an architect or anything else but a violinmaker.”

But Nebel persisted, and entered the Mittenwald violinmaking school in 1953 at age 14. The rigorous four-year program taught him how to build and repair violins, and gave him instruction in everything a violinmaker might need—from accounting to musical composition.

After graduation, Nebel secured a position in the United States, earning only $1.50 an hour but working for the highly regarded Rembert Wurlitzer violin firm in New York. He was supervised by Simone F. Sacconi, whom Nebel considered the maestro of violin restoration. Preeminent violinists, including Isaac Stern, patronized Wurlitzer’s, and Nebel’s reputation grew. After 17 years with the Wurlitzer company, Nebel established his own business.

Nebel’s interest in his work is no less intense than when he started. He begins each day shortly after 7 a.m. and doesn’t emerge from his workspace until 10 at night. He took his last vacation in 1979, although he does spend the weekends with his family, often in the Pocono Mountains.

“I’m a workaholic,” Nebel says matter-of-factly. “Nothing gives me greater pleasure than being in my workshop with my fiddles.”

At the age of 64, Nebel shows no interest in retiring. When he does stop working, he will have his own brand of financial security—dozens of historic, handcrafted violin bows he has bought over the years, some inlaid with mother-of-pearl or gold. Many of the rare bows are worth more than $100,000, and he calls the horsehair collection his “pension.”

However, it is their intricate beauty, not their financial value, that captures Nebel’s heart. “Look at the tip on this one,” he says, holding up a 19th-century bow. “It’s enough to make you weep.”

For now, Nebel will keep fixing fiddles with his sights set on a revered idol—Antonio Stradivari, who hit his prime in his 60s and worked into his 90s.

“All of us would like to outdo Strad,” says Nebel, who jokes openly about his own healthy ego. “We all want to outshine and outlive him.”