The exemplary new Music City Roots series at Loveless Barn repeatedly reveals how American traditional music continues to grow in many different directions. Fittingly, then, this weeks program features masterful acoustic musician Tim OBrien, who at times has seemed to try to embrace every kind of folk music that exists. Live, hell sweep from bluegrass to Celtic to a focus on lyrical ideas common to singer-songwriters. The program also features the folk-rock duo The Believers, the colorful country of Chuck Mead (backed by the acoustic jam band Donna the Buffalo) and the old-school torch music of Kristi Rose and Fats Kaplin. The two-hour radio program, broadcast on WSM-AM and hosted by the superb deejay Eddie Stubbs, is a fine contemporary addition to Nashvilles long legacy of presenting live music over the airwavesespecially at a time when most radio stations are becoming increasingly automated.