Dierks Bentley drifted into predictability on his fourth album Feel That Fire, so his detour into progressive bluegrass on 2010’s Up on the Ridge is a bit of shock.

Ditching much of the polish and precision that encumbered Feel That Fire, Bentley strips back to acoustics and brings in a host of guests, notably the Punch Brothers, who play on a quarter of the album, Miranda Lambert, Kris Kristofferson, and Del McCoury, whose keening voice soars on a cover of U2’s “Pride (In the Name of Love).” The very presence of a U2 song suggests that this is not a traditional bluegrass album, either in its content -- Bentley balances a sharp version of “Rovin’ Gambler” with a terrific rearrangement of Bob Dylan’s “Senor (Tales of Yankee Power)” -- or in its approach, as he sometimes puts picking in the backseat, letting the instruments strum sweetly as he croons.

These cuts may not have the snap of classic bluegrass, but they do give Up on the Ridge a sense of country crossover, illustrating that Bentley is shrewd enough to walk the line between commercial and artistic concerns, but the best testament to his skill arrives on numbers like the loping, bluesy “Bad Angel” (the Lambert duet), the sprightly “You’re Dead to Me,” and flinty, funny “Bottle to the Bottom” (with Kristofferson), songs that draw from tradition with a modern sensibility, illustrating Bentley’s skillful synthesis of past and present.