"It don't mean a thing if ain't got that swing," claimed Duke Ellington. But what does swing mean? In St. Louis, for decades, it has meant Swing Set, the most redoubtable proponent of that most irresistibly danceable of jazz forms. Formed in 2011, the Sidemen — an ensemble that features members of Swing Set, the Orbits, the Lettuce Heads and the St. Louis Ragtimers, for starters — poses no threat to any better-known band or anyone who loves the nimble rhythms and graceful interplay of swing. But it also pushes against the restrictions of any single genre. With Carl Pandolfi on piano, Jon Ferber on guitar, John Marshall on drums, Richard Tralles on bass and Eric Sager on clarinet and saxophone, the quintet is as likely to cover Thelonius Monk, Fats Domino or the theme to The Rocky & Bullwinkle Show as Benny Goodman. The five veterans of the Sidemen know what swing and so much more really means. Find out for yourself at one of its semi-regular haunts — the Maya Café, the Casa Loma Ballroom or Rue Lafayette for Saturday brunch.