Down from the Mountain is a new documentary by D.A. Pennebaker, whose other works include Don't Look Back and Monterey Pop. The subject of the new film was a concert given by some of the musicians on the Oh Brother Where Art Thou? movie soundtrack — which became an unexpected hit. The star of Down from the Mountain is the late John Hartford. Some of the same musicians are giving another concert in New York tomorrow. The film opens in New York on Friday. David D'Arcy reports.