Like Barbara's, our bluegrass group uses an Audio Technica 4033. Great mic. But what really makes it work is a device called a feedback eliminator. The one we use is a Boss AF-70. This peculiar device initiates a search-and-destroy mission when you start it. It tests the response of the room, and notches away those frequencies that cause problems. The result, in a nontechnical description, is that you can boost the volume fairly high, so that the mic picks up very well when you are 2 to 6 feet away. It's great because the 3 singers can stand close enough together to really get those harmonies tight. Our lead instruments can then move in and out to do their breaks.