Here’s a speakeasy tip: Find a red door in the alley. Knock four times. When a person in suspenders and a bow-tie answers say: “Django Does Duluth.” The great prohibition-era guitarist Django Reinhardt won’t be playing there, but a band that’s just as hot will: The Gentleman’s Anti-Temperance League. The five-piece string band features brassy vocalist Kellie Reichert with dueling hollow-body guitar players Daniel Rosen and Alan Peterson, violin player Jonathan Halquist and bassist Peter Whiteman. Their sound celebrates smoky, boozy 1920s jazz swing with their own 21st century originals that make the door-knocking hunt worthwhile.