You might not expect National Review to write about AC/DC and other rock groups, but …

The past four years have been a time of turbulence for AC/DC. There’s been a jailbreak, if you will.

Longtime drummer Phil Rudd was sentenced to eight months of home detention after pleading guilty to threatening to kill a man. Cliff Williams, the band’s bassist since 1977, announced his retirement from music. Brian Johnson, vocalist since 1980, stepped away from touring due to hearing problems. Co-founder and rhythm guitarist Malcolm Young left to treat his dementia, and then passed away.

It appears that Angus Young, the band’s lead guitarist and sole remaining founding member, is undeterred. He will soldier on to create new music and tour with replacements, including Guns N’ Roses frontman Axl Rose. After all, there’s still a strong demand for AC/DC music and a limited supply of lead guitarists who look good in schoolboy uniforms.

Steven Hyden, in his new book Twilight of the Gods refers to the phenomenon as “shrunkgroups.” Lindsey Buckingham can’t commit to a tour? Fleetwood Mac simply recruits Mike Campbell and Neil Finn to suit up for the squad. Glenn Frey passes away? The Eagles tap country star Vince Gill and Frey’s son, Deacon, to fill in.

What’s important is that the machine stays well-lubed and the ticket-buying fans get to hear the songs they’ve been singing along with for decades.

Twilight of the Gods is simultaneously a love letter to a certain collection of artists and songs and a preemptive eulogy for the classic-rock genre, and perhaps for rock music itself. In preparation, Hyden spent a year attending classic-rock concerts across the Midwest, listening to the albums that shaped his youth, and rereading seminal books about the bands and artists. He artfully retraces the steps of a young man falling in love with this music.

The book makes clear early on its subject is not classic rock, but classic rock. What’s the difference?

Clearly, my definition of “classic rock” is shaped by classic-rock radio. . . . The overriding factor in determining who was classified as classic rock — and who was classified as folk, punk, new wave, or metal — was mainstream popularity. If you sold millions of albums, played arenas, and benefited from a major record label plying disc jockeys with cocaine and microwaves in order to get your music on the radio, you were classic rock. If you were beloved by critics, played clubs and theaters, and earned way more street cred than dollars, then you were slotted in one of the ‘cult artist’ genres.

In other words, Styx gets to be “classic rock,” and the opening lines of “Come Sail Away” are chiseled into our collective memories, waiting to be recalled whenever Dennis DeYoung’s piano intro triggers the need. Elvis Costello? Well, he’s “new wave,” so the beauty and power of “New Lace Sleeves” is reserved for those who have taken the time to seek out and explore the tour de force that is the 1981 album Trust.

But what does it all mean now that the most famous and influential purveyors of classic rock are fading away?

“You can’t talk about classic rock now without also thinking about death,” Hyden writes. And, indeed, the rock obituaries have begun to pile up. David Bowie, Tom Petty, Gregg Allman, Glenn Frey, Walter Becker, and J. Geils all have passed away in recent years. Paul Simon, Elton John, and Lynyrd Skynyrd just announced farewell tours, as they say goodbye to the road.

Could the future of classic rock look something like the modern-day incarnation of Foreigner? The band, best known for late-’70s and early-’80s classic-rock cornerstones such as “Cold As Ice” and “Urgent,” now features just one original member in Mick Jones. One other guitarist dates back to the mid ’90s, well after the band’s heyday, while everyone else has been added since 2004.

Over the past few years, Jones has missed quite a few shows due to various health issues — but the shows have not been canceled. At times, the audience is paying pretty good money to see a version of Foreigner in which every band member is, well, foreign to any of its chart success.

Father Time is undefeated; band members will continue to leave this Earth or become physically incapable of touring. Perhaps Mick Jones has stumbled upon the next breakthrough in keeping classic rock alive. At some point in 2033, might we see the officially licensed, Kevin Cronin–endorsed, all-replacement version of REO Speedwagon™ playing the county fair at a town near you? Will Rick Nielsen be lending his signature five-necked guitar to younger version of himself to keep Cheap Trick’s legacy (and money-making prowess) intact?

Hyden spends the final portion of his book grappling with the question of whether or not there will be another generation of fans who even have an interest in rock music. He blames, in large part, a gradual narrowing of the definition of the term, arguing that recent stars such as Taylor Swift and Adele have “rock in their DNA” but never are discussed as other than Top 40 pop artists.

The distribution aspect also is problematic. As Hyden writes, “Life-changing bands don’t just appear on television or the radio these days. . . . The music no longer finds you. You must find the music.” As the “rock star” archetype has faded from pop culture, so have the avenues from which listeners could experience new guitar/bass/drum-centered music.

In fact, as Hyden pointed out in a 2015 essay for Grantland, one of the most successful rock bands of the past decade, The Black Keys, sidestepped the normal channels almost entirely by licensing song after song for commercial use. Think you don’t know The Black Keys’ music? Pull up “Tighten Up” or “Howlin’ for You” and experience flashbacks to any number of television ads you’ve seen over the past few years.

Later in that essay, Hyden puts forth another keen observation, namely that dozens and dozens of bands and artists who would have been considered rock not long ago have been reclassified into the country ecosystem. After all, who is Keith Urban other than Bryan Adams with the occasional banjo or fiddle? A song like “Long Hot Summer” would have absolutely owned rock radio in a different time.

Like Hyden, I grew up on classic rock. I bought all the albums. I read Rolling Stone and spent countless hours devouring books and reference guides about music made years before I was born. I’ve experienced a whole lot of these classic-rock bands in person. In fact, there’s really only one more act I’d truly regret not seeing live before retirement (or something worse): The Rolling Stones.

Come on, Mick and Keith. Back to the U.S. for one more rodeo.

Fans of Chicago have watched guitarist Terry Kath die, bass guitarist/tenor singer Peter Cetera leave for a solo career of ballads more sappy than his former band’s, as well as Cetera’s replacement and multiple other musicians leave, to the point where only four original members are left — keyboard player/singer Robert Lamm, trumpet player Lee Loughnane, trombone player James Pankow and saxophone player Walt Parazaider (who doesn’t tour anymore). They are viewed as Chicago’s core four.

At the risk of appearing equivocal, there are core members of groups, and there are lesser members of groups. Chicago survived Kath’s death and Cetera’s departure, though the group still performs songs sung by their former members:

Led Zeppelin survived drummer John “Bonzo” Bonham’s death, but it likely would not have survived Robert Plant’s death or departure. The Who survived drummer Keith Moon’s death, but it wouldn’t survive the death or departure of Roger Daltrey or Pete Townshend. There has been a debate for years over whether Van Halen was really Van Halen with lead singer Sammy Hagar instead of David Lee Roth. Several musicians have left Electric Light Orchestra, but the only one most people know is Jeff Lynne.