For 20 years, Geert Chatrou worked as a forensic psychiatric nurse at a mental institution in Holland. Day and night he tended to murderers, rapists and criminals deemed “too crazy to go to a prison.”

But on the side — in his free time, on his way home, between tasks, at times when he was not even conscious of his actions — he would whistle. It was a “deviant behavior,” he said, that began when he was about four.

“My dad always whistled around the house,” said Mr. Chatrou. “I think I thought it was part of communication in my family or something.”

But Mr. Chatrou was not just the average whistler. He knew this even as a boy, when nobody really paid attention to his talent. In a family that was always busy playing instruments and making music, classical mostly, his whistling was lost.

Noticed or not, whistling remained a fundamental part of Mr. Chatrou’s life. The hardest weeks of his life, he said, were the three that followed a bicycle accident he had when he was 10 years old.

“I ran into a street lamp so I bounced my lips against that stupid thing and I couldn’t whistle for about three weeks because my lips were swollen up and bruised,” he said. “I was really, really depressed and really angry and I really hated it.

“If I can’t whistle, it’s very difficult,” he added. “Because it’s a way for me to express my feelings or emotions.”

In 2004, Mr. Chatrou’s whistling was taken seriously for the first time. On a whim, his former sister in law entered him in the whistling world championship competition in Louisberg, N.C. He won first place after a whistle-off against the reigning champion.

“It was a joke for her,” said Mr. Chatrou. “She thought, well, he will never go to America to win a contest. But I decided if there was something silly like this, I want to join. So I went to America and then I won.”

Mr. Chatrou’s trip to Louisberg could not have been better timed. That same year, Chilmark filmmakers Kate Davis and David Heilbroner also traveled to Louisberg for the championship in hopes of finding material for an upcoming documentary. Ms. Davis had wanted to make a short film about whistling for years. While jogging, Mr. Heilbroner had the idea to research whistling competitions. When he arrived home, he discovered the Louisberg competition was scheduled to take place in two weeks. The couple decided the airfare was worth it.

“We said two things need to happen: the whistlers have to be really, really good musicians and they have to be incredibly colorful characters, and if they are, there’s a film there,” said Mr. Heilbroner “And we went down and they delivered on both fronts dramatically. The whistlers were so funny and so varied and they were so talented. It opened up a whole world, a bit of Americana history.”

Ms. Davis and Mr. Heilbroner spent the next 10 months constructing a film around the cast of characters they met at the whistling world championship, who ranged from an investment banker at The Carlisle Group. to a turkey caller from New Jersey.

“We thought it was absolutely hysterical, but also very beautiful at times,” Ms. Davis said. “One of the whistlers whistles a Vivaldi aria almost in an operatic way. It’s so beautiful it could bring tears to your eyes.”

The two filmmakers spent hours talking to sound experts and whistling historians, collecting clips of whistling in movies and in history — from Snow White and the Seven Dwarfs performing Whistle While You Work to the Army in Bridge On the River Kwai whistling to keep their spirits up. Ms. Davis and Mr. Heilbroner hoped their documentary would remind people of the “lost art of whistling,” and the range of uses and meanings attached to the skill that is, as Mr. Heilbroner said, “about to be forgotten.”

Their film, called Pucker Up: The Fine Art of Whistling, premiered in 2005. It went on to become a big hit in Europe, and helped launch Mr. Chatrou’s career as a professional whistler. It will be screened on Thursday, July 24, at 7:30 p.m. at the Martha’s Vineyard Film Center in Vineyard Haven.

Since the release of the film, Mr. Chatrou has performed for the queen of Holland twice, in 2005 and 2009, and once for her successor, the king, in 2013. He’s also had symphonies composed specifically for him with an accompanying orchestra.

But fame hasn’t changed Mr. Chatrou a bit.

“I’m still the same Geert as I was 10 years ago and 20 years ago,” he said. “I don’t think anything will change me.”

But one thing is certain, Mr. Chatrou’s days as a psychiatric nurse are long gone.

“Now I’m a free man,” Mr. Chatrou said. “I live like an artist and I like it.”

Pucker Up: The Fine Art of Whistling will be screened at the Martha’s Vineyard Film Center on Thursday, July 24, 7:30 p.m. Filmmakers Kate Davis and David Heilbroner will be in attendance as will Mr. Chatrou, who will give a live whistling performance.