Bluegrass music is a musical form that developed in the south-eastern United States, particularly in the Appalachian region of Kentucky, Virginia, Tennessee, West Virginia, and North Carolina. Whilst it is difficult to say exactly when bluegrass came into being, many consider 1945 to be the crucial year, as this was the year that Bill Monroe added the innovative banjo player Earl Scruggs to his band.
Bluegrass music has its stylistic origins in Appalachian folk music (itself originating largely from Irish and Scots traditional music), blues music, early country music, Baptist gospel singing, and jazz.
The typical bluegrass instrumentation consists of five acoustic stringed instruments: the fiddle, the guitar, the banjo, the mandolin, and the upright bass. Often, the resophonic guitar is included as part of a bluegrass group, in addition to, or sometimes replacing, one or more of the other instruments.