Though not as formidable in number or in impact as the hat acts of the’80s and’90s (Garth Brooks, Alan Jackson, Clint Black, et al.), combos producing a twang-light version of country pop are casting an increasingly large presence on the Billboard country charts and mainstream radio airwaves. Along with groups like Reckless Kelly, Eli Young Band and The Lost Trailers, the Zac Brown Band has recently made the jump from local heroes to contenders for the title of Nashville’s newest greatest thing.