For scholars of indie rock, the union of Mary Timony and Carrie Brownstein as Wild Flag is notable not only for the pedigrees but for what they signify. The former was the voice of Boston lethargy rock band Helium, the latter (along with Wild Flag drummer Janet Weiss) a member of Portland's Sleater-Kinney. And what has the merger wrought? Rock, with guitar solos, mean riffs, barks, yowls, "shoop-shoops," grooves and an inherent understanding of swagger and energy. At its best, as on the masterful "Short Version," which takes a Tom Verlaine-inspired guitar line, dumps it in gasoline and sets it on fire, the fledgling concern races like it's been together for years. El Rey Theater, 5515 Wilshire Blvd., L.A. 7 p.m. Thu. $25. theelrey.com.