Southern Appalachian descendants of 17th century English, Scottish, and Irish immigrants created the American art form we call Bluegrass. Appalachian music is derived from various influences, including the ballads, hymns, and fiddle music of the British Isles (particularly Scotland), and the African music and blues of early African Americans. It is a mixture of several types of music, including old-time, country, and blues, but particularly mountain string bands.
The genre of bluegrass did not emerge until around the 1930s when artists like the Monroe Brothers (led by guitar player Charlie and mandolin player Bill Monroe) began performing as a string band with no percussion. When the Monroe’s’ band appeared on the syndicated radio program Grand Ole Opry in 1939, they introduced bluegrass to legions of country music fans nationwide. Early on, it was often referred to as “hillbilly music”. It was after Bill Monroe, from the Bluegrass State of Kentucky, called his band ‘Bill Monroe and the Blue Grass Boys’ that the music began to be referred to as bluegrass. Bill Monroe, the Father of Bluegrass, also helped launch the careers of other iconic bluegrass musicians, including guitarist Lester Flatt and banjoist Earl Scruggs. Later, Flatt and Scruggs would break off as a duo in 1948 and spread bluegrass music beyond its Appalachian roots.

Bluegrass is traditionally played on acoustic string instruments: guitar, banjo, mandolin, fiddle (violin), and upright bass (string bass). Optional bluegrass instruments include dobro (resonator guitar), harmonica, lap steel, jug, accordion, jaw harp, and various handheld percussion instruments such as washboard, spoons, and egg shaker).

Most bluegrass music is played at a driving pace with a high lonesome sound and generally in a major, not a minor, key. Multi-part vocal harmonies are common in bluegrass music. The lead vocal, usually a high tenor, croons in a high, lonesome sound, while the other singers harmonize in what bluegrass players call a "stack”. Bluegrass makes frequent use of close-harmony. The vast majority of 3-part harmonies are baritone, melody, and the higher harmony. Bluegrass gospel almost always leverages the vocal characteristics of African American gospel.

The folk revival of the 50’s and 60’s brought in new audiences to bluegrass and it began to be thought of as folk music. Although bluegrass had strong roots in the south, it was fundamentally transformed through a 20th century migration of southerners to the industrial centers of the north.