by William RuhlmannIt's a folkie tradition and an economic boon to carry with you tapes to sell at your gigs, and before Shawn Colvin released her first Columbia Records album, Steady On, she used to sell a tape made at an April 1988 show in Somerville, Massachusetts, containing acoustic versions of songs that later turned up on her Columbia releases--"Diamond in the Rough," "Shotgun Down the Avalanche," "I Don't Know Why," and "Knowing What I Know Now," among others. In the studios, such songs acquired arrangements and other instrumentation, which may have made them more commercial, but didn't improve them. Now, Colvin's management has launched Plump Records and released her live tape (with a couple of additions), though her contract with Columbia is still in effect. And guess what? It's still her best recording.