The most revelatory of a three-volume survey of Sun Records (see also Blues Box and Rock Box), this six-CD set comes via Germany’s Bear Family, which has arguably done more to preserve country-music history than any U.S. label. As detailed in the set’s 148-page book, Sam Phillips launched Sun with country as well as blues. And while Elvis Presley, Johnny Cash and Carl Perkins show up here, less-famous labelmates started their own fires by rubbing blues and country together in different ways. Hank Williams and Bob Wills loom on sides by Slim Rhodes, while dazzling singers like Charlie Feathers and Warren Smith highlight the hillbilly in their rockabilly. “Split Personality,” by Smokey Joe Baugh and Bill Taylor, could be the collection’s theme song – a racially confounding mix that distilled the nation’s soul into a seven-inch 45.