Skip McDonald paid his dues long ago. The Sugarhill Gang guitarist helped define hip-hop on classics like “The Message” and “Rapper’s Delight.” A decade back he headed to the blues, linking with On-U producer extraordinaire Adrian Sherwood to explore the dub side of soul. His fourth such project, Champagne & Grits, is the least Jamaicanized, most song-based record yet. Guests Junior Delgado and Ghetto Priest add a bit of island life to McDonald’s emotive guitar, but when Massive Attack vocalist Shara Nelson begs you to “Say My Name,” you’ll truly know what longing is all about.