Whether they’re explaining how to build a guitar or play a Dobro, or singing the sweet harmonies of “Fox on the Run” so that they flow like the river in the song, Bill and Maggie Anderson are the heart and soul of American music, the music that was born in these mountains.

Following the music, they migrated to Fancy Gap from New York, and have settled in comfortably, able to give advice on local campgrounds and festivals.

You’ll find them playing from noon, or thereabouts, to 4 p.m. Wednesdays at the music center throughout the season. They set up there because Bill is an authorized Martin guitar repairman, and also builds instruments himself, including the Dobro that his wife plays and the guitars that he plays. He brings guitar parts and is able to describe how the magic happens. Or take your guitar in for repair.

While he talks to a man about his Martin (“I’m sure there’s a whole lot better guitar here than what you’re hearing”), Maggie is demonstrating the Dobro for a guy who’s interested in learning to play. She goes slowly through one verse of “Go Tell Aunt Rhodie” for him, and tells the visitors how the Dopyera Brothers invented the instrument in the 1920s, trying to make the Hawaiian guitar louder.

“What’s that instrument called?” another visitor asks.

“Do-bro,” says Maggie. “They took the first two letters of their first name and then the first three letters of ‘brother.’”

“It’s a guitar with a hubcap,” her husband wisecracks.

The man who wants to learn Dobro leaves with a hand-drawn chart of notes from Maggie and advice on a learning method. “He shows you where the notes are, and then he does, ‘Are You Washed in the Blood.’” She sits down and plays the notes for the interested student.

Bill, meanwhile, has got the old Martin tuned up and is playing it and evaluating.

Back with the other couple, Maggie is showing how the right hand picks the strings – “after that you’re ready to sit in a jam session.”

Someone else is interested in Bill’s electronic tuner, which he demonstrates. The visitor wants to buy it, but Bill laughs and says he’ll mail him one.

A couple traveling in a camper asks about the Galax fiddlers’ convention.

“What dates in August?”

“The first full week. Just look up the Galax fiddlers on the Internet.” Maggie explains how they will get a better camping situation if they sign up to compete.

“Let’s play a couple songs. Where are you from?” Bill asks some visitors.

They’re from Winston-Salem.

“What kind of music do you like?” Maggie asks.

“A little bit of all of it, but not all of any of it.”

This makes Maggie consider. “I was thinking of ‘Fox on the Run.’” To Bill: “Are you ready? 2-3-4…”

After an instrumental intro, the harmonizing begins.

“Play the ‘Foggy Mountain Breakdown,” a visitor says.

Bill explains that that’s a banjo tune. “Do we know a Flat and Scruggs song?” he asks his wife.

They decide on the old Lester Flatt song, ‘Cabin on the Hill,” which they do in a sort of call-and-response duet.

Someone mentions Doc Watson and they’re off on another duet they learned after jamming once with Doc, “Tennessee Stud.”

The woman from Winston-Salem is impressed. “You guys are good. Y’all have been at it a while, haven’t you.”