This summer would seem to be the Season of the Musical in San Francisco; you can't kick a dog anywhere downtown without disrupting some kind of musical play. Lee Brady's Southern Lights is a "country music romance" that plays like a honky-tonk ballad -- twangy, rueful, and a little damp. Lonn McGee is a lonely singer trying to hold up the rafters of a declining country-western venue called the Crossroads, in East Texas. His ex-girlfriend, Callie, has wandered back to town. In high school they had a semi-incestuous romance: Callie is the daughter of a country-music legend named Cash Callendar who adopted Lonn as a teenager (so they were brother and sister, but not by blood). Ghosts of Callendar and Callie's mom, LouAnn, haunt the Crossroads, and we watch both romances play out in alternating scenes. The characters are involving, but the show lacks energy; original songs by Don Seaver and Julie Jackson would benefit from a live country band. Robin Abbott, as Callendar, looks and sounds the part of a country legend, but he plays guitar the way some actors try to speak German. But Lisa Marie Newton as Callie and especially Leigh Anne Marchesi as LouAnn have sweet, lilting voices; their performances brighten the melodrama. "Oh, Lonnie," says Callie to her sad-sack would-be lover, "why dontcha put that line in a jukebox and charge a quarter for it?"