Bill C. Malone and Tracey E.W. Laird spend much of Country Music USA posing a question they would seem to be uniquely well-positioned to answer: what is country music?

The book, which started life as Malone's doctoral dissertation and was originally published in 1968, has just been reissued in a 50th anniversary edition that also anticipates its moment in the limelight. Next year, Malone will star as the primary historian (think Shelby Foote in The Civil War) in Ken Burns's documentary series on the history of country music.

One of the most fascinating things about the book is that it still holds up because the genre's fundamental existential question, one with profound moral as well as aesthetic implications, is the same today as it was in 1968. What is country music?

The music industry's answer is tautological: it's country music if it gets played on country radio. Malone and Laird, though, suggest that country radio has been stuck in a sort of holding pattern for the past half-century: it rewards artists who are white, politically conservative, and pay lip service to a rural lifestyle while borrowing liberally from mainstream rock (and, increasingly, rap) conventions to appeal to a sizable urban audience as well.

That identity crisis, this mammoth history suggests, dates back even further than 1968: it started in 1955, when the success of Elvis Presley forced programmers, bookers, and record companies to reevaluate all their assumptions about music genres. Country music had by that point settled comfortably into the singing-cowboy model, and Elvis was certainly no cowboy. Yet, with so much of its history, including its songbook, plundered for the newly-designated genre of "rock and roll," could country survive?

The solution was what Malone and Laird call "the Chet Atkins compromise."

Chet Atkins deliberately tried to create a middle-of-the-road sound (his "compromise") that would preserve the feel and ambience of "country" music while also being commercially appealing to a broader audience that had no experience with rural life and no liking for the harder sounds.

That compromise, in the ears of many, was a deal with the devil — sparking a recurring series of "traditionalist" insurrections. There was the folk revival that spotlighted early string-band greats (early '60s), the "outlaw country" of Merle Haggard (late '60s), the youth-driven interest in classic country sparked by Bob Dylan's alliance with Johnny Cash (early '70s), the organized effort to take back the Country Music Association after Olivia Newton-John won that organization's award for Female Singer of the Year (mid-1970s), George Strait's bid to make Texas swing mainstream again (1980s), Uncle Tupelo's "alt-country" movement (1990s), and the outlaw country revival of artists like Miranda Lambert (2000s).

Of course, Atkins doesn't show up until page 300 of a 748-page tome. Malone and Laird diligently lay the groundwork with coverage of early American folk traditions; the ways that recording and broadcast technologies solidified genres, separating "hillbilly" from "race" music; the way that wartime patriotism sharpened listeners' appetites for what sounded like a quintessential American aesthetic; the role of the Grand Ole Opry and other institutions in creating national country stars; and the (inevitable, the authors suggest) supplanting of the hillbilly vibe with one that drew explicitly on the frontier tropes of western expansion.

The authors' authoritative familiarity with country's many sub-genres (bluegrass gets its own chapter) lends them powerful insight into newer phenomena like the "bro country" of Luke Bryan and Sam Hunt.

"Bro country" is a tag for music that sidesteps the potential human depth of country music's thematic bedrocks: family, home, nostalgia, simplicity, love, heartbreak, natural beauty, good-timing, drinking, hard work. Instead, bro country songs string together a formulaic subset of tropes about beer sipping, truck driving, sunglasses wearing, unpaved roads, and tanned girls in shorts, typically building to a predictable catchphrase singsong chorus. In short, it is the contemporary version of country music's recurrent consternation about "realness." Whether from a lack of sincerity or talent, "bro country" connotes a failure to successfully navigate the channel between sincerity and commercial appeal by caricaturing artists as less sophisticated or less capable than their more artistically accomplished peers. For critics, the issue with bro country is not its themes per se: beer drinking and country roads are at the heart of many classic country songs. Moreover, country music tradition depends on set themes, musical timbres, stylistic gestures, and wardrobe cues. Bro country, however, lingers at the shallow end of the pool, never venturing too deep.

For many listeners, today's "Americana" genre encompasses a truer, more artistically interesting, set of artists whose work has evolved along the country lineage than does the bro-heavy "country" genre. "Americana," for example, has no trouble embracing a song like "Daddy Lessons," the Beyoncé number that she later played as a duet with the Dixie Chicks — a group who themselves were ousted from mainstream country institutions after daring to criticize Republican president George W. Bush.

For Malone and Laird, those musicians' "Daddy Lessons" performance at the 2016 CMAs was a gauntlet dropped. Could country music accommodate this African-American woman sharing the stage with politically liberal white women, singing a song that manifestly represented the truest ideals the genre had always claimed to espouse? "It's no contrived genre mash-up," write the authors about the song, "but a powerful assertion that genre divisions are contrived in the first place."

The Current's Bill DeVille is currently at the Americana Music Association's annual festival and conference, where he's hosting a show on Friday.