For some of the best, and I DO mean BEST, gospel bluegrass give a listen to Doyle Lawson and Quicksilver. I had the opportunity to hear them live in a small venue and it really knocked me over it was so good! They have some of the tightest vocal harmonies I've heard and they are exceptional instrumentalists too!
I'm going to have to work on a website of my own that I can actually post snippets of songs and some small video clips of movies and tv, etc. No matter how well you think you are describing something it always falls short of experiencing it yourself.
