Bluegrass traces its roots to the traditional ballads and lively jigs and reels of English, Scottish and Irish immigrants who settled in the rural Appalachia area of the United States (southern New York to northern Mississippi, Alabama and Georgia) in the 18th century. Influenced by African-American blues and jazz, it is played on acoustic (unamplified) string instruments, including the fiddle, banjo, guitar, mandolin and upright bass. Musicians take turns playing and improvising the melody, while the rest of the group provides accompaniment.

Most bluegrass tunes are simple, requiring just a few chords. In contrast, vocal harmonies can be complex, with three or four parts. Themes run the gamut — from coal mining and railroading to religion and murder.

Bill Monroe, regarded as the “father of bluegrass,” formed the Blue Grass Boys in 1939. When banjo player Earl Scruggs joined Monroe’s ensemble in late 1945, his syncopated style kicked the bluegrass sound into high gear.

ORIGINALLY classified as mountain hillbilly and country-western, the band’s rhythmic mix of country, gospel and blues was not formally recognized as a distinct musical style until some 20 years later, when many other groups were echoing the sound. The genre was dubbed “bluegrass” in honor of Monroe, his home state of Kentucky and his seminal band.