A sublimely nuanced, sometimes explosive, dozen-strong juggernaut of Southern roots music, the Tedeschi Trucks Band only begins with the myriad strengths of its husband-and-wife namesakes. Derek Trucks is a guitar savant whose range of expression spans Duane Allman and John Coltrane. Susan Tedeschi, a terrific blues guitarist herself, is a stellar singer who brings together blues, soul, and gospel. Dual percussionists’ slippery cross-cultural rhythms, a bristly horn section, new jazz-savvy bassist Tim Lefebvre, and an experimental streak all contribute to TTB really hitting their stride on January’s Let Me Get By. The songs have a rich, organic feel, sifting among musical elements stretching from the Smokies to the Delta. “Anyhow” is sleek Southern rock laced with gospel and country, Tedeschi unleashing vocals lashed by anguish and yearning. “Don’t Know What It Means” matches funky New Orleans grooves with Muscle Shoals soul, plus a wicked guitar duel and raucous horn jaunt. The dazzling finale, “In Every Heart,” suggests Irma Thomas backed by a Memphis gospel quartet and the Band. Speaking of which, opening will be Levon Helm’s daughter Amy, a fine, gospel-influenced singer.