I know nothing about this recording, but I saw Steve Earle with The Del McCoury Band at The House of Blues in Hollywood, and they performed into a single microphone. They were all playing acoustic instruments (guitars, upright bass, fiddle, mandolin, banjo), also being picked up by the same mic. They were positioned in a semi-circle behind the mic, approximately equidistant from it. When it was time for Steve to sing a verse of a song, he would move in closer to the mic, dropping back when the verse was over; when there were harmony vocals, the harmony singers would move in, then drop back when the harmonies were over; when there was an instrumental break, one of the band members would move in closer, dropping back when done. It was great!