M.D. Anderson helped treat John Prine during his recent bout with cancer. Now the folk stalwart is thanking the cancer center by raising funds in a concert with his neo-folk friend and duet partner Iris DeMent. Prine's wry wit and DeMent's soulful purity make their songs top of the crop, and given that the two singers love to team up, as they did on In Spite of Ourselves, this may add up to three shows in one. When it comes to music for the NPR demographic, this is the finest wine in the cellar.