Bluegrass was started by a fellow named Bill Monroe and was what he called originally "that high lonesome sound." It is essentially the love child of old time country music and Scots highland music. A Scots fiddler would find himself/herself quite comfortable at a Bluegrass jam.
The Appalachian mountains stretch from the Green Mountains in Vermont down through New York where they are called the Catskills down into Pennsylvania where they are called the Appalachians into Maryland where they're called the Catoctin Ridge and into Virginia where they're called the Blue Ridge and into Tennessee and North Carolina where they're called the Smokies. Same range. They are among some of the oldest mountains in the world, and prior to a couple ice ages ago were higher than the Himalayas. Now they are old and tired and worn down by glacier and mostly civilized by cities and highways, but some of the old magic is left. And that old magic expresses itself in music. The very roots of this mountain range can be expressed in the key of C is seems.
The land was settled by Englishmen and Italians and Germans for the most part, but the wilds were expanded into by Scots and Irish. There was so much intermarrying, we actually frequently refer to them as Scoth-Irish ancesters here. No one quite remembers the old timer's nationalities from six or eight generations back. As they moved across the land, expanding the very edge of western civilization facing immeasurable odds and dangers, they brought music with them. The mountains liked the music, and the Appalachians forevermore will be known by the reels and jigs of old-time Appalachian Mountain Music.
Bill Monroe took that music, added some guitar and banjo and some old-time style Country lyrics sung in a tenor voice, and you've got Bluegrass. It's a mixture of personality, music style, leftover magic, whatever instruments were laying about, and geology.
The very best bluegrass band I have ever heard play live was a family band called "The Bluegrass Brothers." You can here samples of them here: http://thebluegrassbrothers.com/ When I went to see them, they did two sets and got two standing ovations from a usually stoic audience that I can only recall ever giving a standing ovation to the goodbye concert done by The Johnson Mountain Boys. I was worried that the mandolin player and the bass player were going to have to be carried off stage. Whatever they had in them, they poured out in their singing and playing.
- Zurf
p.s. I concur on the "Will the Circle Be Unbroken" series. I listen to it frequently. It contains instrumentals and a capela, and everything in between.
p.p.s. A bluegrass concert is likely to be the only spot where you will hear the musicians sing about the lauditory benefits of Floyd Country moonshine and heartfelt worship of Jesus in the same set - knowing the guys on stage are fully aware of each.