BARTON HOLLOWJoy Williams and John Paul White aren't a couple, but they certainly sound like they're in love, singing together with the sort of familiarity that only seems to exist between couples and siblings. On Barton Hollow, their studio debut as the Civil Wars, the two trace each other's melodies with close harmonies that never fail to lose their romance, even on breakup tunes like "Falling." It's an organic, folk pop sound not unlike the one made by the