Zac Brown Band is a little bit country, a little bit rock and roll. They became stars in the late 2000s on the strength of the number one country hits "Chicken Fried" and "Toes," songs that seemed like throwbacks to the country-rock of the '70s. For a while, ZBB continued in that vein, scoring another breezy, beachy hit with "Knee Deep" and underscoring their '70s singer/songwriter heritage with the warm, burnished ballad "Colder Weather," but soon the group proved themselves to be a restless jam band, as eager to crank up the amps as they were to ride a supple groove. This se...