Last week, Joe Corré, the son of the fashion designer Vivienne Westwood and the late Sex Pistols manager Malcolm McLaren, took a small barge out on the Thames and proceeded to set a fortune in irreplaceable punk memorabilia on fire. It was all stuff that had once belonged to his father: one-of-a-kind items of clothing, rare posters, records, and assorted curios, valued, altogether, at more than six million dollars. Corré hoped to make the point that punk’s once-vital energy had long since been tamed by nostalgia, safely absorbed into the British mainstream—as evidenced, most recently, by “Punk London,” a yearlong celebration currently under way throughout the city, marking roughly forty years of punk. This is precisely the kind of establishment embrace that Corré believes his father’s generation, all negation and anarchy, would have gleefully rejected.

You wonder if Corré’s stunt might have aspired to something more positive—selling everything and donating the proceeds to charity, for example. But there was something resonant about his insistence that old forms of youthful rebellion, particularly ones that rely on loud, fast guitars, had run their course. This has become one of rock music’s defining conditions: it now seems anachronistic and provincial, safely and comfortably mainstream even at its most unruly.

And yet there remains an enduring belief in rock’s mystical powers. It’s precisely that fading conviction that makes “Oasis: Supersonic,” a documentary about the Manchester band’s mid-nineties ascent, such a gripping chronicle of what was so clearly another time. Oasis can lay claim to being one of the last generation-defining rock acts, particularly in Europe, where it sold millions of records, became a tabloid sensation, and, at its height, performed a concert that four per cent of the U.K. population tried to attend. Most of the band’s success had to do with the music: massive tunes that toggled between brashness and sentimentality, the biggest hits ready-made for pub sing-alongs. But one of Oasis’s loudest features was how much its core duo, the brothers Noel and Liam Gallagher, loved the rock-and-roll life style. As Liam put it, “I was just obsessed with being in a band. Ob-fucking-sessed, man.” They had discovered that the secret to superstardom is embodying a paradox: they were normal guys, just like their fans, living a dream on behalf of the masses. It could have been anyone. Yet they would never miss a chance to remind you that what was happening could never be repeated.

Music documentaries like “Supersonic” generally trace an epic arc of rising and falling, and at this point the Gallaghers have their stories down cold. They were born to a warm, understanding mother and a distant father, from whom they would eventually become estranged. The brothers grew up in a council estate in Manchester, fiercely aware of their class status. Later, this would prompt them to lash out at other bands as “middle-class bastards” (Blur) or “a boring bunch of fucking students” (Radiohead) who had grown up with pomp and privilege. But, as youngsters, the brothers’ working-class background only fuelled their dreams of something else, anything else. For a while, Noel’s only plan for escape was as part of the road crew for the Inspiral Carpets, a local band that would embark on modest tours of far-flung lands. Liam just disappeared into the music, working humdrum jobs, buying a record and some weed at the end of the week, and, as he explains with a gauzy reverence, “getting soaked in it.”

So much of the brothers’ mythology rests on their profound love of rock music. This seems simple and obvious, but how many artists, after reaching the celebrity stratosphere, just seem to go through the motions? It’s entrancing to hear Liam and Noel describe what it meant for them to make music of their own. “Once I discovered weed and guitars, and you’ve gone into another world, what would you want to go out for?” Noel recalls. “Everything I ever wanted in life was coming out of the speakers.” Liam admits. “We weren’t the best musicians. But we had spirit, man.”

As they rose, that spirit was enough. Mark Coyle, a friend of the band who went on to engineer its first album, “Definitely Maybe,” recalls not having a clue what the band’s début single, “Supersonic,” was actually about. “No, I didn’t understand what ‘feelin’ supersonic’ meant. But I’m with you, whatever it is. I’ll die for you right now. That’s how I felt about Oasis.” The Gallaghers’ music was flagrantly derivative of their record collection, but that perfectly suited the stories they told about themselves. While their friends were out on the town, they had spent thousands of hours practicing, studying their favorite songs by the Beatles and T. Rex, taking them apart and putting them back together. The film includes an interview conducted shortly before the release of “Definitely Maybe,” in 1994, in which the brothers distill their entire working philosophy, by describing their début. “Twelve songs that are about being alive and having a good time. About being happy, about enjoying yourself,” Noel says, stone-faced, before a pensive Liam butts in: “And then about being sad but knowing it can get better.”

It can be tedious listening to artists promote their own genius and salute their own hard work. But the Gallaghers do it masterly. “You are in a political situation even if you don’t realize it,” Noel says of those early days spent perfecting their craft. “ ‘Cause that is the battleground, that is the essence of politics: accommodation, food, and trying to make a living.” As I watched “Supersonic,” I kept pausing it in order to scribble down quotes like these, which seemed to contain eternal wisdom about what it’s like to come from nothing and then see earlier versions of yourself among your fans. Noel says of their 1995 album, “(What’s the Story) Morning Glory?,” “The songs on that record, they’re extraordinary songs. And they’re not extraordinary songs because of anything that I did. I only wrote them and we only played them. It’s the millions of people who fuckin’ sing them back to you to this day that have made them extraordinary.” Much of “Supersonic” depicts Oasis as a band that sought only to return what music had given it: a language for love and compassion, for living forever and living inside cheesy sentiments that look clumsy on the page but feel momentous in an arena; a model for coming together, even as the brothers’ relationship crumbled in real life.

One of the executive producers of the movie, which was directed by Mat Whitecross, is Asif Kapadia, whose previous work includes "Amy," the stirring chronicle, largely culled from never-before-seen home videos, of the late Amy Winehouse's rise to superstardom. One of the strange things about watching “Amy” is realizing that someone had the foresight to bother filming so much of her everyday life, back when the odds were against her making it to the top. In her absence, we’re left with tape, endless possibilities, and a story over which she had no final approval. In contrast with “Amy,” “Supersonic” is a story told with the benefit of hindsight and an awareness of narrative completion.

And for all its fetching moments of banter and bluster, “Supersonic” doesn’t stick the landing. As the band begins its gradual descent, the absences in this version of its story become more obvious. There’s no mention of Blur, Oasis’s chief rival, or of the other musical genres that began to colonize Britain’s youth; the film doesn’t dwell on the drugs or on Tony Blair, whom Noel posed with in a famous photo op engineered to establish the young Prime Minister’s Cool Britannia bona fides. The members take turns lamenting the coming dawn of “celebrity-driven culture,” the eventual dominance of talent shows and reality TV, and the rise of the Internet for disturbing the sanctity of what they had done.