Bluegrass music is a genre of American roots music that developed in the 1940s in the Appalachian region of the United States. The genre derives its name from the band Bill Monroe and the Blue Grass Boys. Bluegrass is traditionally played exclusively on acoustic instruments and has roots in traditional English, Scottish, and Irish ballads and dance tunes as well as in blues and jazz.

Here are some key features of bluegrass music:

• Instruments: Bluegrass features acoustic stringed instruments such as the guitar, double bass, fiddle, five-string banjo, mandolin, steel guitar, and Dobro.

• Timing: Bluegrass emphasizes the off-beat and notes are anticipated, creating a higher energy characteristic of bluegrass.

• Melody: In bluegrass, one or more instruments each takes its turn playing the melody and improvising around it, while the others perform accompaniment.

• Vocals: Bluegrass makes frequent use of close-harmony duets, trios, and quartets. Its vocal range is rather high, forcing vocalists into their upper ranges and creating a tight, almost austere, sometimes called "high lonesome" sound.

Bluegrass music developed from elements of old-time music and traditional music in the Appalachian region of the United States. The Appalachian region was where many Scottish American immigrants settled, bringing with them the musical traditions of their homelands. Hence the sounds of jigs and reels, especially as played on the fiddle, were innate to the developing style. Black musicians, meanwhile, brought the iconic banjo to Appalachia.

Bluegrass music is now performed and enjoyed around the world. The International Bluegrass Music Association claims members in all 50 states and 30 countries. In addition to the classic bluegrass style that is still performed widely, bluegrass bands today are influenced by a variety of sources from jazz to Celtic music.