Almost nobody sticks to doing just one thing around here. It seems like every player’s also an aspiring producer, and all songwriters itch to perform for fans of their own. Even so, it’s hard enough to find even one guy who’s first-rate at picking, singing, songwriting and entertaining, much less two. That’s one reason Tim O’Brien and Darrell Scott drift into duo mode every few years or so; they’re quadruple threats who’ve found each other. Plus they can both summon thoroughly down-home sounds (especially when they sing harmony), scare up a limber groove and inject a bit of wit to the proceedings. O’Brien and Scott have already done the studio thing together. This time they’re releasing a new live album — We’re Usually a Lot Better Than This — drawn from a pair of freewheeling acoustic shows they played in Asheville in the mid-Aughts.