As a child growing up in Bulgaria, Guenadiy Lazarov was mesmerized by great accordionists tearing off serpentine melodies over uneven Balkan rhythms, as they played for tips at weddings and parties.

“The accordion was king — there was a special respect for the instrument in our culture,” said Mr. Lazarov, who runs one of the last accordion repair shops in the New York City area.

The Accordion Gallery, his small showroom and repair shop in a nondescript house in New Jersey, is where many of today’s accordion kings — from polka stars to Charlie Giordano, an accordionist who plays with Bruce Springsteen — go to have their instruments maintained and repaired.

Mr. Lazarov began playing the accordion when he was 10 and continued to play professionally on the side even while pursuing a career in physics.