For those interested in the single mic technique used by some bluegrass performers, the Bluegrass Wales website has an interesting article posted about this much used technique.
The article covers the history and techniques involved in using a single mic for live bluegrass performance. The article begins with a history of the microphone and progresses through a discussion of current day uses. It covers the type of microphones currently used for the technique, along with answers to typical problems with the technique, and performance tips for bands wanting to employ the technique in their stage show.
The article is well thought out and well written. Take 10 minutes and read it at BluegrassWales.org.