To the left of the cash register is a room where the walls are lined with a few hundred acoustic guitars, mandolins, banjos and violins of all brands and styles. In another, larger room, some 600 electric guitars surround floor space that is divided into rows of amplifiers, drum kits and keyboards. The store’s stringed instrument inventory is at about 1,000 — the same number as its stock of firearms. “The difference between the two,” Mr. Decosse said, “is that anyone can learn to shoot a gun, but not everyone can learn to play an instrument.”

Mr. Decosse himself sings and plays guitar, piano and fiddle. He is a member of the Busco Bandits, a group that performs country music and oldies. In the mid-1970s, customers who knew of Mr. Decosse’s musical abilities asked him to sell guitar strings, picks and capos. He said by 1976 he had added some Gretsch guitars, hanging them over the meat counter. From there, he expanded, building more than a dozen additions to the original structure.

Visitors who enter what appears to be a rambling mom-and-pop convenience store are “shocked in a good way to find something like this in the middle of nowhere,” he said.

Today, musicians from all over visit Dick’s, including Doyle Dykes, a finger-picker; Jerry Donahue, a guitarist with the Hellecasters; and Michael Angelo Batio, a guitarist in the 1980s glam band Nitro.

Image Rifles are among the 1,000 firearms for sale at Dick's. Credit... Nathaniel Brooks for The New York Times

Eric and Leigh Gibson, of the bluegrass group the Gibson Brothers, are regulars. They grew up on a dairy farm down the road from Dick’s and took banjo and guitar lessons there. Eric Gibson worked at Dick’s in the early 2000s, struggling to pay bills while an album he and his brother recorded in Nashville languished.

“Dick Decosse has always been encouraging, he’s always been there for me,” Eric Gibson, who lives in nearby Brainardsville, said. “When I didn’t know what to do and things were just not working out, he said, ‘Even if you’re moving in the wrong direction you need to keep moving. It’s better than standing still.’ ”