CHARLESTON, S.C. — The Ebony Hillbillies, the New York City-based string band performed on an outdoor stage at Spoleto Festival USA, an annual international festival of opera, dance, theater and music, on a night so muggy that at one point fiddler Henrique Prince looked heavenward and remarked, “Barometric pressure.” Surrounded by Spanish moss-draped live oaks, the Hillbillies delivered a rousing lesson in the history of traditional, black string music from “Altamont” and “Pateroller’ll Catch You” to Bonaparte’s Retreat” and “Liza Jane.”

“Documented fiddling by black players goes back to the 1600s in New York,” Prince said. “And nobody but black players played a banjo until the early part of the 19th century. They were all handmade instruments.”

The banjo, of course, came to these shores from West Africa, where it was fretless and made from a gourd. The African version of the fiddle has one string.

“String music is the folk music of Africa, not drums,” Prince said.

A New York subway platform institution since the late 1980s — find them at Times Square, Grand Central Station and 34th Street at Macy’s — the Ebony Hillbillies have also played at Lincoln Center and Carnegie Hall and for the International Bluegrass Music Association in Nashville. They influenced the formation of the other premier black string band, the Carolina Chocolate Drops.

The Hillbillies’ current incarnation includes Newman Baker on a lap washboard, outfitted with tiny cymbals, that he plays with shotgun shells on his fingers; Bill Salters, two-time Grammy winner and composer of “Just the Two of Us,” among other hits, on stand-up bass; Gloria Gassaway on bones and vocals; and original members Norris Bennett, a former full-time recorded street musician, on banjo and mountain dulcimer, and Prince.

Prince (call him Rique, “just don’t call me late for supper,” he said) was born in Harlem and grew up in Queens. His father played guitar, lap steel and piano; an uncle played saxophone in calypso bands. Prince played “the radiator” at a young age, he said, then learned violin, followed by trumpet, tuba and guitar. He studied jazz and classical violin and then discovered the history of the African American fiddle/banjo duo tradition and its development into the black string band of the late 1800s and early 1900s. He found 20th-century recorded musicians such as fiddler Cuje Bertram and three-finger-banjo player Murph Gribble.

“It was important to have a fiddler on the plantation not only because the master liked the fiddler to play for dancers but because it kept the morale of the slaves up,” Prince said. “This has all been lost in our history but it’s an important part of it. Black musicians played for white people and they played for themselves. And they had to learn everything in order to play for people with the most money. They learned German music and Dutch music and English music.

“This music was real popular, and then the jazz era took over and string band music became ‘country music.’ If you see a photograph of an early jazz band, right in the center of it is a banjo player and a fiddle player.”

Those players switched to guitar, horns became more popular, and changing tastes and the commercialization of recorded music put African-American music into jazz and blues categories, while country music evolved into white bluegrass and Nashville pop.

But “this is American music,” Prince said. “At one time, there was a lot less difference between black and white culture in America. It was universally American. A lot of our leaders today are trying to separate people. I guess it’s good that we’re around to show that we’re not that far apart, still.”

The group has recorded two albums — “Sabrina’s Holiday” and “I Thought You Knew” — and a third, “Barefoot and Flying,” will be released this summer.

They are not a “museum band,” Prince emphasized “The black string band of the 19th and early 20th century was improvisational,” he said. “Some of the ideas sound very funky and very modern.: The Hillbillies continue that improv tradition and channel blues and jazz riffs. They include Marvin Gaye’s “Sexual Healing” as part of their repertoire.

“We’re trying to do this in the most sophisticated way we can,” Prince said. “We want to make the music as if it never stopped.”