Few groups have covered more musical territory in the name of accessibility and broad appeal than Zac Brown Band. They grew from a regional phenomenon to a national and international one a dozen years ago, breaking through as a breezy, frequently jammy country-rock band—the only outfit of its kind in the contemporary country field of the late 2000s. Led by the amiably ambitious Zac Brown (and rounded out by fellow singing, songwriting instrumentalists Coy Bowles, Clay Cook, Jimmy De Martini, John Driskell Hopkins, Matt Mangano, Daniel de los Reyes, and Chris Fryar), the group established a stylistic range that was simultaneously conversant in down-home textures and classic-rock flourishes and omnivorous in its embrace of current pop forms. On The Owl, Brown and his cohorts stretch out even further. Among the pop flourishes: a songwriting assist from Shawn Mendes (on “Someone I Used to Know,” a rueful guitar-driven reminiscence accented with zigzagging electronic patterns), production input from gurus including Ryan Tedder and Jason “Poo Bear” Boyd (on “Need This,” a new-school, countrified beach jam that’s more bustling than laidback), and a guest appearance by Brandi Carlile (Brown’s duet partner on the billowing breakup ballad “Finish What We Started”). Brown has described the album as having a more personal bent, and he puts himself out there in openly emotional or confessional postures on tracks like the piano ballad “Leaving Love Behind.” But he and his bandmates also show how experimental they can get, turning in effects-savvy postmodern jam band performances during the blues-rocking “Shoofly Pie” and the country-rocking “Me and the Boys in the Band,” and delivering a melting pot of spaghetti-western twang, Eagles-esque harmonizing, and sleek, rhythmic R&B gloss during “Already On Fire.”