A basketball stadium isn’t the place one would normally expect to hear Americana, but that’s the sort of thing that’s happening now. So Brooklyn, be prepared for the moment when the Barclay’s Center becomes one big barn when the Avett Brothers and Old Crow Medicine Show come around on tour. The Avetts are in a celebratory mood, and for good reason: their latest album, Magpie and the Dandelion, is one of their finest. Elmore’s Keith Hadad called it “timeless, akin to Music From Big Pink or After The Gold Rush.” Old Crow also bring a good, crowd-pleasing show, and their version of “Wagon Wheel” is still a stone-cold classic. Both bands are sure to bring the sizable house down.