Nostalgia is a funny thing.

It inclines us to romanticize the past, elevating our memories of people, places, and events to a level of excellence that surpasses our original experiences of them. It's nostalgia that turns a middling movie from the mid-'90s into a "classic" that you watch fondly every time you stumble on it while flipping through the cable channels. You didn't much like it at first. But now it's somehow better than it used to be. Put that dollop of nostalgia together with lots of other happy little memories, and the past itself can begin to seem better than the present. Suddenly you're living through an era of decline, sliding down a well-greased slope toward a mud puddle of mediocrity.

Or maybe you're just getting old and grumpy.

Okay, okay: Maybe I'm just getting old and grumpy. But I swear popular music was better when I was growing up in the 1970s and '80s. It was the heyday of rock music — a new form of popular art that was rapidly expanding in scope, with different artists stretching in various directions, constantly testing the limits of the possible.

Inspired by the musical and lyrical boundary-smashing of The Beatles and Bob Dylan, countless bands and artists experimented with new, more intricate compositional forms. Songs got longer and more complex, with lyrics aspiring to literature and music moving beyond familiar rhythm-and-blues patterns to find inspiration in orchestral music and jazz. Musicianship became more refined and accomplished.

And the ambition! Sure, some of it seems ridiculously pretentious in retrospect. That's what happens when artists experiment and push into new territory: They sometimes fall flat on their faces. But at other times, they soar. The rock operas, concept albums, art rock, glam rock, and prog rock of the era was the expression of a restless drive to create something genuinely great — something lasting, ecstatic, transcendent. A statement.

That kind of rock is virtually extinct today, and not just because tastes have moved away from arrangements built around electric guitar. Contemporary pop music sounds impeccable, but less because musicianship has improved than because advances in digital recording technology have made it possible to eliminate imperfections and achieve inhuman standards of flawlessness in every vocal line, drum fill, and guitar solo. The result is pristine. But also antiseptic. Bloodless. Songwriting, meanwhile, has reverted to an updated version of the pre-rock Brill Building model, with committees of pros called in to collaborate on sugary confections packed full of hooks and custom designed to top the charts. It's pop music as advertising jingle.

I don't so much dislike today's hits as listen to them with indifference. They're pleasant and catchy enough. But it's background music to my life rather than a source of life, or beauty, or joy.

Something has changed, and it isn't me. How do I know? Because I've just discovered the contemporary Canadian band Big Wreck, and they're every bit as great as the best bands of my youth — and nothing like what sells records today. Big Wreck's new album Grace Street, in particular, is a rock 'n' roll masterpiece the likes of which I haven't encountered in many years.

Just about everyone who writes about the band describes them as "underappreciated." And so they are. Formed by Ian Thornley in 1994, they scored some modest success with a post-grunge debut album In Loving Memory of… (1997), which spawned the minor hits "The Oaf (My Luck is Wasted)" and "That Song." After their second album fizzled commercially in 2001, Big Wreck disbanded while its founder formed the alternative-metal band Thornley, which released two unsuccessful albums of its own in 2004 and 2009.

It was only when Big Wreck re-formed in 2010 that the band began to make music on the highest levels. Roughly half the songs on Albatross (2012) combined a lean, aggressive sound with a sparkling melodic flair that had surfaced only very rarely on their earlier releases. ("Wolves" sputtered as a single, but it's a fabulous song and one of the album's strongest tracks.) Next, Ghosts (2014) took a quantum leap forward, breaking enormous musical ground. The songs were now longer and more complex, with stunning displays of virtuoso musicianship, as the band careened through jarringly dissonant verses in off-kilter meters to reach breathtaking, expansively tuneful choruses. (A live performance of "I Digress" provides a taste of this new surging sound.)

But Grace Street is the band's greatest achievement yet. Over the course of 13 tracks and nearly 70 minutes of music, Big Wreck shows that they can do just about anything: elaborate epics as thrilling and unpredictable as anything from the heyday of art rock; dead-on homages to the mid-career Rolling Stones, Physical Graffiti-era Led Zeppelin, and (on the album's first single) the early '80s arena rock band Asia; exquisite Beach Boys-inspired vocal harmonies; riff-driven songs in indecipherable time signatures; gorgeous, intricately layered ballads; even a 7-minute instrumental that sounds like a distant cousin to "YYZ" by fellow Canadian prog-rockers Rush.

If Nirvana pioneered the quiet-verse/loud-chorus dynamic that defined grunge, Big Wreck have mastered a potent variant of angular and ugly verses that give way to spectacularly melodic choruses, with bridges that often introduce a whole new section, or alternative chorus, to the song. The artist who's come closest to modeling this oscillating approach to song structure is probably Peter Gabriel, especially on his remarkable string of self-titled albums from the late '70s and early '80s.

This distinctive song-form may be put to most effective use on Grace Street's opening track, "It Comes As No Surprise." Beginning with a plaintive melody sung at the very top of Thornley's range, it passes briefly through a gratingly haunted section that's the harmonic equivalent of primal scream therapy before finally resolving into a richly textured dream-like meditation cushioned by multi-part vocal harmonies. Then the cycle repeats. That the lyrics of these sections recount the vicious fights and doomed reconciliations that preceded Thornley's recent divorce only makes it more powerful.

None of these musical accomplishments would be possible if Big Wreck weren't a stunningly proficient and versatile band. Thornley's closest collaborator from the beginning has been rhythm guitarist Brian Doherty. Bassist Dave McMillan and drummer Chuck Keeping joined only after the band got back together, but by now they've been fully integrated and seem eager and willing to push themselves further with every new record. Finally, Paulo Neta adds another rhythm guitar to the aural assault.

But the key to Big Wreck's achievement is Thornley himself. He leads the band. He writes the songs. He handles lead guitar, throwing down solos that range from lightning-fast buzzsaw atonality to a soaring melodicism reminiscent of Pink Floyd's David Gilmour. And he sings, spectacularly, with a voice that seems capable of rising precisely as far into the stratosphere as any melody requires for maximal impact.

Big Wreck is the total rock 'n' roll package.

For a taste of Grace Street at its most surprising and impressive, settle into the nearly eight-minute epic "A Speedy Recovery." It begins with an tightly coiled vamp of a verse, with McMillan and Keeping locked in an intense bass-and-drums groove. Eventually the tension gives way to a solid, tuneful chorus. Each repeats once more before the entire song shifts sideways into a glorious alternative chorus that introduces an entirely new harmonic palette with multiple contrapuntal backing vocals. That is followed by a long, impressively restrained guitar solo that slowly builds toward a reprise of the two choruses in reverse order. The song is exhilarating.

Like the band itself.