"If you're honest and open, he will write you a song," sings Zac Brown in "Martin," an ode to his acoustic guitar. Honesty and openness are articles of faith for Brown, whose smash 2008 single, "Chicken Fried," made him an overnight country star. He specializes in high-earnest homespun: woodsy songs with three-part-harmony vocals and lyrics full of folksy homilies. Brown is a fine guitarist who sings with husky warmth, and the ZBB have jam-band chops and a songwriterly knack for hooks. But just when you're starting to enjoy the sound, another of Brown's two-bit life lessons — "Hear what the land has to say/Quiet your mind" — hits with a thud.