Should you ever stumble upon an Old Crow gig in the Southeast, you'll know you've happened upon some happily bizarre alternate reality, where beer-guzzling twentysomethings routinely pack clubs and go nuts over... authentic-sounding Appalachian string-band music. ''OCMS,'' their first disc to be distributed nationally, may be too modest to spark a bluegrass revolution on every American campus. But as produced by Gillian Welch's partner, David Rawlings, it strikes a fine balance between a rowdier acousticism and the more reflective folk traditions exemplified by, well, Welch.

