Steve Weber, the guitarist of the Holy Modal Rounders, a cult psychedelic folk group that grazed the pop-culture mainstream with a song featured in the 1969 film “Easy Rider” and influenced generations of underground musicians, died on Feb. 7 at his home in Mount Clare, W.Va. He was 76.

His death was announced by the Davis Funeral Home in nearby Clarksburg, which did not give a cause.

The Holy Modal Rounders emerged in New York in 1963 as a duo, with Mr. Weber on guitar and Peter Stampfel on fiddle and banjo. Like countless others swept up in the folk revival of the time, they were inspired by the traditional songs in the “Anthology of American Folk Music,” compiled by the filmmaker and historian Harry Smith in 1952.

But while most of their peers approached old material with reverence, Mr. Weber and Mr. Stampfel stood out with their spontaneity and almost boyish mischief. On their first two albums, released by the folk label Prestige in 1964 and 1965, they freely rewrote lyrics to 1920s songs like “Blues in the Bottle” and “Bully of the Town,” and sang gleefully with a peculiar kind of nasal harmony.

Their antics did not endear the band to folk purists, although Mr. Weber, who grew up in rural Bucks County, Pa., was noted for his mastery of traditional guitar styles.