San Francisco talks a big game about its folksy leanings, but what have you done lately to conjure the frontier spirit besides drink beer out of a mason jar? Never fear: The Great American Music Hall's got your city-slicker back with its second annual Winter Formal, an evening dedicated to bridging that amiably loping Bakersfield sound and the peculiar melancholy unique to the lonesome crowded west circa 2014. Headlining is the North Bay duo the Easy Leaves, whose deceptively easygoing ditties, as heard in finest form on last year's American Times, churn along on a propulsive undertow and a soft pedal steel moan. Also on the bill: San Francisco honky-tonk quintet the B-Stars and velvet-voiced Sonoma trio the Bootleg Honeys. Something to remember the soul of the state by once all the easy has left for good.