Dave Rawlings sings sweet and country. His hat’s not as high as some but it’s perfectly clean and cream. He plays that 80-year-old guitar like it’s gonna take him away to another planet.  At once caressing it, then tugging and working it round a solo to within an inch of its life. When Gillian Welch sings, her straight, wide mouth hides the smooth and effortless sound that escapes it. There’s no confusing whose voice that is. She smiles frequently, at us, at Dave, enjoying herself and the music they’re making. It’s Dave’s name on the bill, but on stage the two are equals. One wouldn’t be without the other. Gillian jokes that it’s going to get hot and sweaty, which is just as well because that’s how they like it. For sure, the night is still and the old hall is an oven full of bodies. The guitars are pretty high, the jeans straight and not-too-narrow, and the denim double. Americana for the clothes as well as the tunes. Long dresses brush ankles, all checks …