WHAT is country music? Is it a sound: an acoustic guitar, a pedal steel, a fiddle, a high lonesome croon? Is it regional art — and if so, what region, exactly? (Nashville? Appalachia? Bakersfield, Calif.?) Is it a grand tradition, stretching from the Carter Family and Jimmie Rodgers, to Roy Acuff and Hank Williams, to Johnny Cash and Dolly Parton and George Jones, down to the present day? Is country a way of life? A worldview? The best answer might be that country is music that can’t stop defining itself — the genre that can’t stop asking “What is country music?” The latest philosopher to tackle the problem is Brad Paisley, one of modern Nashville’s biggest stars, and greatest talents. In “This Is Country Music,” the title track from Mr. Paisley’s forthcoming ninth studio album, he offers a theory: country is what other pop music isn’t. It’s down-to-earth, not trendy; it prizes realism over artifice; it’s steeped in traditional values — old-time religion, the old folks at home, Old Glory. “It ain’t hip to sing about tractors, trucks, little towns, and mama/Yeah, that might be true,” Mr. Paisley sings. “But this is country music/And we do.” Mr. Paisley excels at cleverly tweaking genre clichés, and “This Is Country Music” is a typically nifty twist: it’s a song about the glory of genre clichés, an unformulaic celebration of formulaic songwriting. It is also, as it happens, a savvy career move. In the dozen years since his 1999 debut, “Who Needs Pictures,” Mr. Paisley has built a huge, hugely loyal fan base by mixing traditional craftsmanship and pop flash, while earning a reputation as Nashville’s quickest wit and most fleet-fingered guitar hero. But on his last studio release, “American Saturday Night” (2009), Mr. Paisley stepped outside of country orthodoxy, with songs that hailed New York City’s multicultural mosaic, extolled the wonders of high technology and tipped a Stetson to newly elected President Obama. By the standards of hip-hop or punk rock, it was gentle stuff. But for a country audience that leans right politically and zealously polices the boundaries of authenticity, it was challenging. “ ‘American Saturday Night’ was sort of was my ‘The Times They Are A-Changin’ album,” Mr. Paisley said recently, speaking by phone from his home outside Nashville. “It was, you know, telling the choir to think outside the box. “But it didn’t feel right to do that again,” he said, referring to the new album. “We’re not asking people to go places where it’s not comfortable. ‘Cause at some point, the choir’s gonna go to another church.” On “This Is Country Music” (Arista Nashville) Mr. Paisley is once again preaching to his choir. It’s a bright, brisk record, packed with the polished country-pop songs that Mr. Paisley’s devotees have come to expect. It’s a study in the politics of 21st-century Nashville stardom, the delicate maneuvering that a performer like Mr. Paisley must do to keep his pews filled. But listen closely and you hear some surprises — and a more expansive definition of country music than the album’s title track at first suggests. Crowd-pleasing is clearly on Mr. Paisley’s mind. “This Is Country Music” is something close to the platonic ideal — or at least an Arista Nashville executive’s ideal — of a Brad Paisley album, hewing closely to a blueprint he’s followed on previous releases. There are big statements (“This Is Country Music”), love songs (“New Favorite Memory”) and a duet with a platinum-selling platinum blonde (“Remind Me” with Carrie Underwood). There’s a honky-tonking lament about hard luck and heavy boozing (“Don’t Drink the Water”). There’s a gospel standard, and an instrumental showcasing Mr. Paisley’s fearsome picking. And there are a handful of the funny novelty songs for which Mr. Paisley is famous. Not all of these hit the mark. “Be the Lake,” about a guy ogling a woman on a waterfront dock, recycles a lusty joke that Mr. Paisley told to greater effect on his 2007 hit “Ticks.” What is absent from “This Is Country Music” is a big risk, like the one Mr. Paisley took with “Welcome to the Future,” the arena rock-style anthem that celebrated Barack Obama’s election. (Mr. Paisley performed the song at the White House in July 2009, one week after its release as a single.) Before “Welcome to the Future,” Mr. Paisley had had 10 straight No. 1 country hits, a record that stretched back four years. But the song stalled at No. 2, snapping Mr. Paisley’s streak. That may have been coincidence, but it’s clear that some of Mr. Paisley’s fans were turned off by a song that saluted the nation’s first black president — and, perhaps worse, a Democrat. “Country music fans have their beliefs and leanings,” Mr. Paisley said. “Somebody on Twitter said, ‘I can’t believe we’ve lost Paisley to the left.’ I was like: ‘I didn’t know I was anybody’s to lose.’ But I knew that the song would be misunderstood.” The new album takes care to reassure old fans, but a hard tack to the right isn’t Mr. Paisley’s style. The title of his current single, “Old Alabama,” suggests a gruff redneck anthem, a song for Lynyrd Skynyrd or Montgomery Gentry. But it turns out to be a cheery exercise in revivalism: a tribute to Alabama, the group that dominated country charts in the 1980s. The chorus interpolates a melody from Alabama’s 1982 smash “Mountain Music,” a stunt that Mr. Paisley suggested is “the closest that country has come to sampling.” (“I was jealous of the Black Eyed Peas,” he explained.) Then there’s “Camouflage,” a galloping rave-up that pokes fun at the prevalence of camouflage as a rural fashion statement. (Mr. Paisley sings: “You can blend in, in the country/You can stand out in the fashion world/Be invisible to a whitetail/And irresistible to a redneck girl.”) Mr. Paisley’s guitar solo quotes “Dixie,” but in the third verse, he suggests jettisoning the Confederate flag for “another way to show your southern pride”: a camouflage flag of “green and gray and black and brown and tan.” It’s a lyric that typifies Mr. Paisley’s ecumenical instincts, striking a compromise between old-fashioned regional pride and modern-day racial sensitivity. It’s also an example of one of Paisley’s signature songwriting tricks: his knack for turning jokes into social commentary, and vice versa. But Mr. Paisley cares less about cultural politics than narratives: the stories, the telling details, that capture the texture of middle-class lives. On “This Is Country Music,” the songs turn on small moments: a glance between lovers, a father brushing his young son’s teeth, a cellphone call taken by a man caught in rush hour traffic. “This is real/This is your life/In a song,” Mr. Paisley sings in the title track, and his vision of “real life” is broader than stereotypical country subject matter. His back catalog includes hits about saintly grandparents and off-roading in pickup trucks — and also songs about Internet chatrooms and reality TV. Like many country singers, Mr. Paisley boasts about his provincialism, but he’s a closet cosmopolitan. Country has always been less walled-off than it lets on. From Ray Charles and Elvis Presley to Garth Brooks and Taylor Swift, the conversation between country and the pop mainstream has been going on for decades. Today, Nashville is the favorite refuge for rock stars looking to revive their careers. (The guests on “This Is Country Music” include Don Henley and Sheryl Crow.) Even pop stars are getting into country carpetbagging. Justin Bieber recently teamed up with the chart-topping country balladeers Rascal Flatts; Rihanna dueted with Sugarland’s Jennifer Nettles on the Academy of Country Music Awards. Last week, Beyoncé released a cover version of Lee Greenwood’s bombastic “God Bless the U.S.A.,” a song Mr. Paisley name-checks in “This Is Country Music.” The influence flows both ways, of course; there’s lots of pop in Mr. Paisley’s big melodic hooks. But listen closely to his new album and you’ll hear more: mariachi, surf rock, Ennio Morricone, Beatles chords, Beach Boys harmonies. Mr. Paisley’s rippling guitar solo in the song “This Is Country Music” begins by quoting the opening strain of one of the masterpieces of classical piano repertory, the “Heroic” Polonaise. Tractors, trucks, little towns, mama — and Chopin? Turns out, that’s country music, too.