A bluegrass jam session at the Old Furniture Factory in Round Hill. The building’s owners have put the property on the market and are hoping the music tradition will continue after the sale. (Jim Barnes/For The Washington Post)

On the last Friday of every month, musicians converge on the Old Furniture Factory in Round Hill, toting stringed instruments of all sizes, from mandolins to upright basses. Before long, they are standing in small clusters, picking and singing, filling the room with strains of bluegrass and old-time country music.

For 14 years, the informal sessions have attracted singers, instrumentalists and fans from the Washington area and beyond. But the future of the jams is uncertain. The Old Furniture Factory is for sale, and bluegrass enthusiasts fear the music will end when the building changes hands.

The yellow, two-story, board and batten building in Round Hill’s small downtown dates to the mid-1880s, when the Howell Brothers Furniture Emporium opened there, co-owner Wally Johnson said. Over the years, the building has housed several incarnations of general stores and even served as a school in 1912 after the town’s previous school burned down, he said.

Johnson and his wife, Carolyn Kruger, bought the building in 1985. He used it as a woodworking shop, and they opened the Round Hill Arts Center there in the late 1990s. Now it’s the base of operations for Johnson’s cabinetry and kitchen design business.

Johnson said he hopes the jam sessions will continue after the building is sold.

“We haven’t made that a condition of the sale,” he said. “We made our desires known, but we’re going to sell the building regardless. . . . My wife and I are in our mid-70s, and it’s time. We need to get our finances in order.”

Johnson said he would prefer that the new owner use the building as a community center that would serve western Loudoun, which he admitted was “a very long shot.” But he also suggested another, more likely possibility that might keep the music going.

“A brewpub would be ideal,” he said. “That would be a perfect marriage, a win-win for everybody.”

The jam sessions started in 2003 as an offshoot of an even longer-running series of weekly bluegrass performances at a Leesburg senior center, Johnson said, adding that he and his wife were inspired to start hosting the sessions after enjoying a similar bluegrass jam in Floyd, Va.

The Round Hill sessions are unstructured — less a performance than a gathering of friends, old and new, who mix and match, forming impromptu groups to make music. At any time, several groups may be playing simultaneously in any of four rooms, where one might hear blues, jazz, Celtic and old-time string band music, as well as bluegrass. In good weather, they spill out onto a large back porch.

“It’s wonderful all the way around,” said upright bass player Carol Manuel of Winchester, who has been coming to the jam sessions since they started. “I haven’t seen anybody that’s been able to duplicate it yet.”

Guitarist Dale Roethlisberger, of North Bethesda, Md., said the jam sessions attract musicians from as far away as North Carolina, Pennsylvania and Georgia.

Fiddle player Vance Bonner comes even farther. An educator and author, she said she travels every year from her home in Oregon to spend her summers in the Washington area “just for bluegrass music.”

“It would be so nice if whoever wants to buy this place wants to keep the music going, because this is a hugely important jam for all the bluegrassers,” Bonner said.

“What’s nice about it is that it’s true jamming,” she added. “People come and they can have a drink in the back yard, and the kids can run around. There’s old folks and young folks, and old beginners and young, advanced kids.”

Guitarist Rich Rodgers of Hamilton said he was a beginner when he started coming to the jams a decade ago.

“I could play chords at that time, but I was self-conscious about playing in public with a group,” he said. “But they’re all so helpful. It doesn’t matter what skill level you are, from expert to just a beginner. You’re welcomed.”

When asked what would be lost if the sessions end, Rodgers replied without hesitation: “The best part of my life. This is a very rare thing.”