Abigail Washburn refers to herself as an old-time musician, having mastered the traditional clawhammer banjo technique and a just-rough-enough voice. Her husband, Bela Fleck, uses fast and complex finger-picking, straddling a line that leans closer to jazz than traditional bluegrass or folk.

“We’ve had to work hard to find each other in terms of matching up on timing,” Mr. Fleck said during an interview at the Old Whaling Church on Tuesday, a few hours before the couple went on stage. “Bluegrass tends to pick up and almost rush. Old-time sort of sits in the groove and is funky. I’m always having to slow myself down while Abby has to lean on the front a little bit.”

“I think we’re fortunate that we’re quite different,” Ms. Washburn added. “What ends up happening in our sets is more unique than if we were both the same.”

Unique, as Ms. Washburn said, is correct.

Later, on stage, one banjo seemed to issue a call that the other would answer, building on each other until they found their pace and sunk into a groove. And once they found it, the notes wrapped around and cut through each other — merging the two banjos into one large and complex instrument.

Mr. Fleck and Ms. Washburn met in Nashville at a square dance in which she was dancing and he was playing his banjo. They were both part of the bluegrass scene in the city, which Mr. Fleck said was smaller than one would think.

At one point in the show, Ms. Washburn sang a folk song in fluent Chines. — Ray Ewing

“She had a boyfriend at the time who played mandolin and their band asked me to play on a record for them,” he recalled. “We got to be friends…and when they split up, at a certain point I asked her out.”

That was in 2003 and the two have been performing together ever since, adding two new members to their tour group along the way — six-year-old Juno and 13-month-old Theo.

Their variance in style, they said, is key to what makes their music appealing to a variety of audiences.

Both musicians have traveled extensively in their careers, gaining influences from the deep south, eastern Europe, New York city and Boston. At the concert, Ms. Washburn even sang in Chinese, which she learned while studying at Colorado College and a brief stint in China, wielding her rare fretless banjo engraved with Chinese calligraphy on the ebony-wood neck.

Another song Ms. Washburn said she picked up from an elder of the Appalachian mountain singing community. “[I] learned this song in a hot tub, in the holler, from Ginny Hawker,” she told the audience.

Though she added her own twist, she said the song has roots that stretch back to the early 1600s.

Ms. Washburn said she gravitated to music rather late. She picked up the banjo during her senior year at Colorado College and never thought she would play professionally until she was approached by a record label in Tennessee.

“She was something rare,” Mr. Fleck said. “Someone who sang with a certain authenticity while playing the banjo in an old-time style. Record labels were like, oh, this is what we need.”

Mr. Fleck started at a much earlier age. One of his first influences was the dueling banjos scene in Deliverance, which came out when he was 14. Soon after, his grandfather gave him his first banjo. After high school Mr. Fleck moved to Boston, playing “wherever the bluegrass was happening that night.”

Throughout his years performing, he said he has experienced a massive cultural shift that has brought the banjo out of obscurity in the eyes of the public. He believes mainstream culture, like he himself, first gained an interest in the instrument after the release of Deliverance.

“It was a number one pop hit, the banjo instrumental,” he said. “But it had a lot of positive and negative impact. It was positive because a lot of people were introduced and started to love the sound of the banjo. But it was negative because people connected it to a very hillbilly culture.”

It has taken a long time for Bela Fleck and Abigail Washburn to shed the hillbilly connotation that is associated with the banjo, though he said there is nothing wrong with “hillbilly” musicians such as Earl Scruggs and Lester Flatt.

“To shortchange it and reduce it to this one little piece, though a beautiful piece of the banjo story, is kind of a lie,” he said.

The history of the banjo, they said, started in Africa before it was brought to the United States aboard a slave ship. The slaves weren’t allowed to have drums for fear they could be used in a rebellion, but the banjos were seen as a less threatening instrument.

The plantation owners made the slaves perform for them, Ms. Washburn said, and often forced them to integrate their music with Irish or other cultures of music — mixing it into the jambalaya of American music history.

Since then the banjo has woven its way through most genres of music, and the two musicians have tried their best to touch on each moment of it throughout their musical careers.

“The banjo is in the center of the whole early moment when music was starting to really happen in its own way,” Mr. Fleck said. “It’s all mixed up in a way that is very complicated to extricate and explain.

During the show, no explanation was needed other than the musical mastery displayed on-stage. The complexity of the history was evident in each note, filling the pews of the Old Whaling Church, and traveling outward through the open windows on a timeless summer evening.