“From Here to the Moon and Back,” the pledge of eternal devotion (with Dolly Parton) that opens Willie Nelson’s conceptual collection of duets with women, has major wedding-dance potential. But several of the pairings that follow lament unions that couldn’t work. Nelson’s partners, sometimes updating songs he cut years ago, span the country spectrum from folk to pop. Weepers and waltzes prevail, but standouts push beyond that: Shelby Lynne’s Western swing, Alison Krauss’ dark Latin tinge, Wynonna Judd’s husky honky-tonk blues, Mavis Staples’ Bill Withers soul cover. And Nelson holds his unmistakable own throughout, like no other 80-year-old could.