Dierks Bentley is one of Nashville's best singer/songwriters of the 2000s, and part of his appeal lies in his casual display of his deep roots, how he built upon Waylon and Merle without ever seeming overly indebted by their legacy; it made him sound grounded, while his sentiments and crisp, clean sound made him seem modern. Bentley doesn't abandon this synthesis on his fourth studio album, Feel That Fire, but he does streamline and simplify it, reining in the ragged country elements and revving up the fist-pumping guitars in an apparent attempt to push beyond the country charts and into some kind of heartland rock crossover. This isn't a huge leap for Bentley, who has never been a roughneck, but he's best when he gets back to his roots and sounds as inventive and vigorous as he did his previous three albums -- when he teams up for a duet with Patty Griffin on "Beautiful World," when he co-writes with Rodney Crowell on "Pray," and, especially, when he teams up with Ronnie McCoury and his band for a rampaging, intoxicating bluegrass closer, "Last Call." These are full-blooded, substantive songs, the kind that linger in the memory.