Bluegrass music is a form of American roots music.
Bluegrass was inspired by the music of Appalachia. It has mixed roots in Scottish, Irish, Welsh and English traditional music, and also it was influenced by the music of African-Americans through incorporation of jazz elements.
Immigrants from England, Wales, Ireland, and Scotland arrived in Appalachia in the 18th (and in some cases 17th) century, and brought with them the musical traditions of these countries. These traditions consisted primarily of English and Scottish ballads— which were essentially unaccompanied narratives— and dance music, such as Irish reels, which were accompanied by a fiddle.Many older Bluegrass songs come directly from the British Isles.
Bluegrass is traditionally played on acoustic stringed instruments. The five-string banjo, fiddle, guitar, mandolin, and upright bass (string bass) are often joined by the resonator guitar (also referred to as a Dobro) and (occasionally) harmonica. This instrumentation originated in rural dance bands and is the basis on which the earliest bluegrass bands were formed.
A sampling of the Five String and the Blue Grass style. http://www.youtube.com/watch?v=GXcRI0BdioE&feature=related (341 days ago)