Rock music isn't dead, but it's barely hanging on.

This is true in at least two senses.

Though popular music sales in general have plummeted since their peak around the turn of the millennium, certain genres continue to generate commercial excitement: pop, rap, hip-hop, country. But rock — amplified and often distorted electric guitars, bass, drums, melodic if frequently abrasive lead vocals, with songs usually penned exclusively by the members of the band — barely registers on the charts. There are still important rock musicians making music in a range of styles — Canada's Big Wreck excels at sophisticated progressive hard rock, for example, while the more subdued American band Dawes artfully expands on the soulful songwriting that thrived in California during the 1970s. But these groups often toil in relative obscurity, selling a few thousand records at a time, performing to modest-sized crowds in clubs and theaters.

But there's another sense in which rock is very nearly dead: Just about every rock legend you can think of is going to die within the next decade or so.

Yes, we've lost some already. On top of the icons who died horribly young decades ago — Brian Jones, Jimi Hendrix, Janis Joplin, Jim Morrison, Elvis Presley, John Lennon — there's the litany of legends felled by illness, drugs, and just plain old age in more recent years: George Harrison, Ray Charles, Michael Jackson, Lou Reed, David Bowie, Glenn Frey, Prince, Leonard Cohen, Tom Petty.

Those losses have been painful. But it's nothing compared with the tidal wave of obituaries to come. The grief and nostalgia will wash over us all. Yes, the Boomers left alive will take it hardest — these were their heroes and generational compatriots. But rock remained the biggest game in town through the 1990s, which implicates GenXers like myself, no less than plenty of millennials.

All of which means there's going to be an awful lot of mourning going on.

Behold the killing fields that lie before us: Bob Dylan (78 years old); Paul McCartney (77); Paul Simon (77) and Art Garfunkel (77); Carole King (77); Brian Wilson (77); Mick Jagger (76) and Keith Richards (75); Joni Mitchell (75); Jimmy Page (75) and Robert Plant (71); Ray Davies (75); Roger Daltrey (75) and Pete Townshend (74); Roger Waters (75) and David Gilmour (73); Rod Stewart (74); Eric Clapton (74); Debbie Harry (74); Neil Young (73); Van Morrison (73); Bryan Ferry (73); Elton John (72); Don Henley (72); James Taylor (71); Jackson Browne (70); Billy Joel (70); and Bruce Springsteen (69, but turning 70 next month).

A few of these legends might manage to live into their 90s, despite all the … wear and tear to which they've subjected their bodies over the decades. But most of them will not.

This will force us not only to endure their passing, but to confront our own mortality as well.

From the beginning, rock music has been an expression of defiance, an assertion of youthful vitality and excess and libido against the ravages of time and maturity. This impulse sometimes (frequently?) veered into foolishness. Think of the early rock anthem in which the singer proclaimed, "I hope I die before I get old." As a gesture, this was a quintessential statement of rock bravado, but I doubt very much its author (The Who's Pete Townshend) regrets having survived into old age.

It's one thing for a young musician to insist it's better to burn out than to fade away. But does this defiance commit the artist to a life of self-destruction, his authenticity tied to his active courting of annihilation? Only a delusional teenager convinced of his own invincibility, or a nihilist, could embrace such an ideal. For most rock stars, the bravado was an act, or it became one as the months stretched into years and then decades. The defiance tended to become sublimated into art, with the struggle against limits and constraints — the longing to break on through to the other side — merging with creative ambition to produce something of lasting worth. The rock star became another in our civilization's long line of geniuses raging against the dying of the light.

Rock music was always a popular art made and consumed by ordinary, imperfect people. The artists themselves were often self-taught, absorbing influences from anywhere and everywhere, blending styles in new ways, pushing against their limitations as musicians and singers, taking up and assimilating technological innovations as quickly as they appeared. Many aspired to art — in composition, record production, and performance — but to reach it they had to ascend up and out of the muck from which they started.

Before rock emerged from rhythm and blues in the late 1950s, and again since it began its long withdrawing roar in the late 1990s, the norm for popular music has been songwriting and record production conducted on the model of an assembly line. This is usually called the "Brill Building" approach to making music, named after the building in midtown Manhattan where leading music industry offices and studios were located in the pre-rock era. Professional songwriters toiled away in small cubicles, crafting future hits for singers who made records closely overseen by a team of producers and corporate drones. Today, something remarkably similar happens in pop and hip-hop, with song files zipping around the globe to a small number of highly successful songwriters and producers who add hooks and production flourishes in order to generate a team-built product that can only be described as pristine, if soulless, perfection.

This is music created by committee and consensus, actively seeking the largest possible audience as an end in itself. Rock (especially as practiced by the most creatively ambitious bands of the mid-1960s: The Beatles, The Rolling Stones, The Kinks, and the Beach Boys) shattered this way of doing things, and for a few decades, a new model of the rock auteur prevailed. As critic Steven Hyden recounts in his delightful book Twilight of the Gods: A Journey to the End of Classic Rock, rock bands and individual rock stars were given an enormous amount of creative freedom, and the best of them used every bit of it. They wrote their own music and lyrics, crafted their own arrangements, experimented with wildly ambitious production techniques, and oversaw the design of their album covers, the launching of marketing campaigns, and the conjuring of increasingly theatrical and decadent concert tours.

This doesn't mean there was no corporate oversight or outside influence on rock musicians. Record companies and professional producers and engineers were usually at the helm, making sure to protect their reputations and investments. Yet to an astonishing degree, the artists got their way. Songs and albums were treated by all — the musicians themselves, but also the record companies, critics, and of course the fans — as Statements. For a time, the capitalist juggernaut made possible and sustained the creation of popular art that sometimes achieved a new form of human excellence. That it didn't last shouldn't keep us from appreciating how remarkable it was while it did.

Like all monumental acts of creativity, the artists were driven by an aspiration to transcend their own finitude, to create something of lasting value, something enduring that would live beyond those who created it. That striving for immortality expressed itself in so many ways — in the deafening volume and garish sensory overload of rock concerts, in the death-defying excess of the parties and the drugs, in the adulation of groupies eager to bed the demigods who adorned their bedroom walls, in the unabashed literary aspirations of the singer-songwriters, in mind-blowing experiments with song forms marked by seemingly inhuman rhythmic and harmonic complexity, in the orchestral sweep, ambition, and (yes) frequent pretension of concept albums and rock operas. All of it was a testament to the all-too-human longing to outlast the present — to live on past our finite days. To grasp and never let go of immortality.

It was all a lie, but it was a beautiful one. The rock stars' days are numbered. They are going to die, as will we all. No one gets out alive. When we mourn the passing of the legends and the tragic greatness of what they've left behind for us to enjoy in the time we have left, we will also be mourning for ourselves.