The gumbo that is today’s New Orleans pop culture includes frozen daiquiris, Drew Brees jerseys, goth eyeliner — and all-American rock band Cowboy Mouth. Since 1990, frontman Fred LeBlanc and his crew have been winning fans with high-energy, soul-cleansing live performances that demand an audience’s sweat and participation. The band’s appearance at Knuckleheads is the second date on its 16th Annual Rock ‘n Roll Mardi Gras Tour and coincides with its latest release, Because the Marching Bands Will Roll, an EP teeming with N’awlins classic covers. Much like the Barenaked Ladies or a fried-shrimp po’ boy, Cowboy Mouth wraps hot, salty guts in easygoing white-bread-and-mayonnaise charm. The result: a feel-good show that goes down smooth and starts off the new year just right.