It’s a tale that plucks the heartstrings.

A new documentary being filmed, “Joe’s Violin,” chronicles how an instrument bought on the black market by a Holocaust survivor in postwar Germany is now lovingly played by a 13-year-old girl in the South Bronx.

Joseph Feingold, 92, grew up in Poland, the eldest of three boys in a Jewish family of music lovers. “My mother sang Jewish songs, and I’d accompany her on the ­violin,” he said.

When the Nazis and Soviets invaded Poland in 1939, Feingold, then 16, was imprisoned in a war camp in Siberia for 6¹/₂ years. His younger brother and mother died in concentration camps.

After the war he was freed and returned to Poland, but after “barely” surviving the infamous Kielce Pogrom on July 4, 1946 — where at least 42 Jews were murdered — he fled to conquered Germany with his father. There they reunited with his middle brother, Alexander, who had survived Auschwitz.

It was in a flea market in Frankfurt, where he lived in a displaced-persons camp waiting for passage to the United States, that he swapped a carton of American cigarettes for a beautiful violin in 1947.

“At that time, the only thing that mattered more than dollars was American cigarettes,” Feingold said. He carried the violin to New York the following year, where he graduated from Columbia University and worked as an architect, settling on the Upper West Side.

He’d still regularly dig out the memento of his old life and recreate the classical music of his childhood, often playing with his grandchildren. But about six years ago, his fingers were no long­er as nimble and the violin was stowed away — until Feingold heard about a WQXR 105.9 FM charity drive last year and ­donated his violin.

TV producer and documentarian Kahane Cooperman heard the story on the radio and wondered who would get the instrument. “I loved that two unlikely people were going to be connected by the violin,” she said.

In February, seventh-grader ­Brianna Perez was selected as the lucky recipient. She has played the violin since the age of 5 at Bronx Global Learning Institute for Girls, a charter school where the instrument is compulsory.

The first time she played it, “It felt like happiness going through your veins, just a joy feeling,” ­Brianna said. “It makes me feel better. When I’m sad or ­angry, I have something to look forward to — I can play the violin.”

She lives with her single mother, a medical-records worker, in The Bronx and plans to audition for music high schools next year. “I’m hoping to become a forensic anthropologist and a violin teacher,” she said.

Next week, Joe and Brianna will finally meet. “The only thing I’ve been thinking of is just giving him a big hug,” she said.