In theory, Thorne Lounge (4260 SE Hawthorne Blvd., 234-2423, thornelounge.com) is a rock-’n’-roll bar. Right now, though, the vibe is more adult contemporary. It’s open-mic night, and at the moment two twentysomethings in striped sweaters are on the small corner stage with acoustic guitars, performing songs that’d probably sound great coming through the house speakers at Pottery Barn. “This is a cover,” they announce, before strumming out a totally straight-faced, utterly funkless rendition of “Billie Jean.” If it weren’t for the crimson-colored walls decorated with images of Marilyn Monroe and the Beatles, light fixtures apparently purchased from an opium den’s yard sale, and signs advertising drink specials with names like Red Headed Slut and Sloe Comfortable Screw (a mixture of sloe gin, Southern Comfort and orange juice that tastes like spiked Hawaiian Punch), it’d be easy to think you’d wandered into a Christian singles mixer. Like the duo currently sucking the soul out of Michael Jackson, Thorne is sincere in its desire to transform the formerly nondescript Vertigo Pub into an authentic neighborhood dive, but it’s an inaccurate cover. A dive is where people go to hide; Thorne has too many windows, and the place is too small to look away in embarrassment when someone onstage is being a bit too earnest.