DURANGO, Colo. — Every summer night throughout the American West, hundreds of tourists and western music fans sit down to a meal and a show at a modern-day chuck wagon. At these venues, a throwback to the covered wagon kitchens that were part of cattle drives, audiences polish off plates loaded with meat, baked beans, a potato, applesauce, a biscuit and cake, and then watch a house band tell corny jokes and play cowboy songs popularized by people like Roy Rogers and Gene Autry in the 1930s and ’40s. The bands are not just the entertainment; they are the main...