As for the concept of "Bluegrass" it is to my ear that old Scottish and Irish tunes played as "Old-timey" (usually simplified and repeated ad-nauseum for dance music) in the US was taken by Bill Monroe in the '30s and played faster (and with more skill) with the "grace" notes reinserted and the keys changed. But unlike the Irish and Scottish originals, Old-Timey and Bluegrass styles lend to a sameness. As the old joke goes, "What's the difference between one Bluegrass tune and another?" Answer, "The name of the tune."