There really aren't any Celtic roots of bluegrass that you could trace as a musical progression. Bill Monroe, the “Father of Bluegrass Music,” was of distant Scottish heratige, visited Scotland, and wrote a babpipe-sounding instrumental piece called Scotland but that's about as many roots as there are.

Bluegrass music owes far more to African Americans than to Celts or Anglos. It was the African Americans who began the fiddle traditions that were picked up by the “old-timey” string bands to form one strand of the bluegrass influences. Monroe actually considered himself a blues singer and, as a young man, accompanied the black Kentucky ragtime/blues musician, Arnold Shultz.

Even though some bluegrass instrumentals have been constructed on melody lines of Celtic origin, the most obvious sounds that contribute to bluegrass owe more to jazz (Earl Scruggs), blues, popular songs, and nineteenth century heart songs than to Celtic music or peoples.

      - Mark