There are bands who make records you love, and which enrich your life or expand your vision and your mindset, which open you up to new ways of thinking or feeling. And then there are bands that not only do all that, but go one crucial and massive step beyond, and actively change your life. If you've ever had a more than passing acquaintance with the music of Fugazi, it's pretty much a given that they will fall into that second category.

They have always been so much more than a band, so much more than a group of musicians making records and playing gigs: have come to mean so much more than "just" the outfit that revolutionised the scene they sprang from and instigated genres, styles and attitudes towards music, musicians and the business of scratching a living from doing what you're good at. Whether it's the vegan, straight-edge lifestyle that the members adhere to (but don't browbeat or proselytise for), the epitome of the do-it-yourself independent ethic they espouse through the running of the Dischord label and the championing of fellow Washington DC artists, the pledge to play all-age gigs at affordable ticket prices which saw them accidentally pioneer the idea that bands could play in unusual spaces, or the steadfast commitment to remain independent which saw them turn down a proffered blank cheque from at least one music-business legend, Fugazi have and will always mean more than the often politicised, sometimes enigmatic and always relentlessly inventive music they released.

Lest my regular reader fears this series is turning into a kind of autobiography by proxy, I ought to get clear from the outset that I didn't give up alcohol because of Fugazi. I can't even say that the band or their peerless discography were part of a direct process of cause and effect that led me to take that decision. The reasons for that had little to do with music, or culture. Whether it's a character flaw or a personality trait, I find it far easier to cut out than to moderate, and, faced with clear evidence (ballooning waistline, incipient general lack of wellbeing), a stark choice presented itself - either pack in the beer, or stop eating pizza and chips. It was no contest, really. All that said: the key experience that gave me the confidence to think that stopping drinking was a viable option came early in 2000, when I met a number of straight edgers, all in their teens and early 20s, and had the opportunity to talk to them about why they'd stopped drinking and the differences it had made to their lives. Without exception, they had each made that lifestyle choice at least partly under the influence of either Fugazi or Ian MacKaye's previous band, Minor Threat. So even if the route was more roundabout, then, I have to say that this band changed my life - and for the better. What follows, therefore, can't really be considered a dispassionate or entirely objective appraisal. You have been warned.

And yet, all that having been said, it would be as wrong to try to consider Fugazi's music as an adjunct to or spin-off from a worldview as it would be to ignore all that context entirely. Thinking of Fugazi as some sort of esoteric left-wing cult with a rock band attached has led to a number of unnecessarily unhelpful misrepresentations - the most pervasive being that they're grim and humourless, makers of monolithic slabs of music intended for similarly inclined ideological puritans. The very fact that when they released an album on coloured vinyl (End Hits, in 1998) they chose to press it on grey vinyl certainly suggests that those who believe them too po-faced to send themselves up are somewhat wide of the mark. The band may have come to mean so much more than "just" music, but if the music hadn't been as remarkable and striking and individual as it was and remains, none of that other stuff would matter.

Repeater wasn't their debut, but it was the first true flowering of Fugazi that made it on to record. The band had almost been willed into existence: such was the love for MacKaye's first outfit and his next band, Embrace, that he was constantly being asked when he'd get back to making music. The route to Fugazi began in 1986 when MacKaye began working with bassist Joe Lally in a trio eventually completed by former Rites of Spring drummer Brendan Canty. They made their first two EPs (the self-titled seven-tracker released in 1988 and the following year's Margin Walker, later released as a single CD called 13 Songs) with Canty's former RoS bandmate Guy Picciotto contributing as a second vocalist. Apparently taking his cue from watching how Flavor Flav had pioneered the role of the "hype man" in hip hop, Picciotto had initially seen his job as being to act as a vocal foil to MacKaye and a visual lightning rod on stage: the shots on the cover of the first EP and the image that appears through the lettering on the sleeve of Repeater come from this era, with Picciotto upside-down on stage, a mic in his hand, shirtless. But by the time the band entered Don Zientara's Inner Ear Studios in Arlington with producer (and then aspirant chef) Ted Nicely for the sessions that would result in Repeater, Picciotto was also playing guitar for the band. His initial concern that he'd duplicate MacKaye's playing was erased by the discovery that he could use his guitar like he used his voice, to offer a different tone and pitch and to complement rather than consolidate what was already there.

The record was recorded mostly in the mornings, so that Nicely could be finished in time to attend classes in the afternoons. (Making an album as, if you will, an appetiser to a main course in culinary training clearly did Nicely no harm: his studies went well enough for him to be unable to work with the band on their next album, the perhaps not entirely coincidentally named Steady Diet Of Nothing, due to him by then having secured a job as a chef.) Unlike the first EP, which band members reportedly felt a duty to release to placate friends and fans who sensed a need for it to be out rather than felt driven to make for its own sake, and unlike Margin Walker, which had been recorded in London after a long and arduous European tour and with the band on the cusp of burnout, everyone seems to have felt that Repeater marked the start of something special. With a couple of exceptions ('Merchandise' appears on First Demo, a 1988 recording released last November) the songs were the product of jam sessions and hadn't been played so much live by the time the album sessions took place that the band were already sick of them.

All these factors, to an extent, sound like they were brought to bear on a sound that is crystalline yet sinuous, where the meticulous precision has been achieved without having the material dulled by the work that has to have gone in to getting the performances and the arrangements ready to be recorded. It certainly sounds like a product of daytime rather than a record made in the witching hours - the sound of bright light rather than dark night. On the occasions this writer has had the privilege to see Fugazi live, they played under plain white lamps, and if memory serves the settings were constant - not just a single colour of light, but no change in the level of brightness. The effect was to focus attention on the music and the performance. The same thing was achieved in the studio and there is a sense that this kind of intensity of intended audience attention was being fed back into the creation of the record. How else can we explain its relentless drive and compulsive clarity?

For those who keep returning to this music, each time we do it sounds completely fresh and alive, even as we realise that performances this focused and drilled can only have been achieved after considerable hard work by all involved over an extended and intensive period. Even when the arrangements are relatively traditional - take 'Reprovisional', for instance - it is clear that plenty of thought and care was spent on ensuring that the dynamics grab and retain the attention, yet the end results feel natural, vibrant, alive, rather than premeditated or mechanical or rote. Rock music tends to reward the inspired accident: fans have become trained to respond to sounds that may be calibrated to micron-thin tolerances but which give the aural appearance of the intuitive and the inspired. That isn't what seems to be happening here. Nor is this the product of a jazz sensibility, where technical excellence and deep understanding of chords, tone and rhythm combine to permit improvisation, in tune and on time, to provide the hypnotic focus. On these sessions Fugazi sound like they found a new path, somewhere between the two - where you can hear the deliberation behind every note yet never for a second feel that this makes the music anything less than tremendously exciting.

It's not a sound without precedent. For all that Fugazi represented a series of giant leaps from the music the band members had made before the group formed, there are other points of reference that feel as though they're valid. In his chapter on Fugazi in the excellent Our Band Could Be Your Life: Scenes From The American Indie Underground 1981-1991, Michael Azerrad astutely notes the influence of The Ruts. For all the kinship felt between punk and reggae, few bands really found a way of amalgamating the musics in an ongoing way: a cover version or two was one thing, but The Clash (another obvious Fugazi influence) took until Sandinista! before they managed to sublimate the ingredients into a cohesive new whole. It may be that Fugazi didn't get all the way there until Steady Diet..., where a song like 'Reclamation' makes the melding of a bass line that could work in reggae with a guitar onslaught worthy of Sonic Youth at their most overwhelming sound like the most natural partnership imaginable. But on the closing 'Shut The Door' it's the sense of space in the groove that bears evidence of reggae's influence: a sparseness to elements of the arrangement that gives the guitars room to range around the vocal. Even at this stage it's clear that the band are forging something new.

It's also a very democratic sound, apparently at times to such an extent as to have held development back. In particular, his determination that Fugazi was to never become "Ian MacKaye's new band" meant that the person who might otherwise have become the group's natural leader was reluctant to take up the mantle. As a result, a kind of paralysis of politeness became a risk, no-one wishing to upset the balanced dynamic by speaking against another member's musical idea. You'd have to have been in the rehearsal rooms and studio sessions, indeed would probably have had to have been simultaneously inside each band member's head, to know exactly whether this was ever a problem, or just a perceived potential problem: to the outsider, the result is to lend the music a degree of collaborative cohesion all but unheard of anywhere else. In songs like the title track, we never get a sense of an "After you," "No, after you" ballet of good manners: instead, the two guitars, vocal lines, bass and drums are each allowed to take charge at different points, and that sense of constant change in which is driving the train along helps to ensure a unifying inner harmony to the structure that means the songs sound like nothing that had come before, even as they draw on elements that come from elsewhere.

And into this unprecedented and absorbing sound, Fugazi poured lyrics of depth and weight: all that sound and fury was never going to be allowed to signify nothing. There is, of course, an enigmatic quality to some of the writing, allowing the listener to make their own interpretations and for the music to come to mean something individual and personal, even amid the hooks and choruses designed specifically for communal involvement and shared release. Some songs are obvious, but others remain occluded - and each individual listener may end up putting different songs into each category. 'Reprovisional' is perhaps this listener's best example of a song where the meaning seems elusive, like trying to remember a dream - to others it might well read as a more straightforward piece about backsliding politicians. 'Sieve-Fisted Find' is another where the power of what's being sung is enhanced by the ability of the words to carry more than a single pre-defined interpretation: the idea of desperately trying to hang on to something that is slipping through your fingers can apply to an enormous range of different situations, so perhaps the imagery itself is the only thing that matters.

The record does have clear lyrical themes, though, and, since they are indivisible from the way the band members chose to live their lives and conduct their business, they come through loud and clear and often. 'Merchandise' is an unambiguous declaration of independence - a song that you sense pretty much could not have been written today, in a world where building a cottage industry like Dischord from scratch has become almost unimaginable given the reticence so many supposed "fans" of music seem to have when it comes to paying for a new record. There were no Fugazi T-shirts or tour posters, just CDs and LPs. And when MacKaye bellows "We owe you nothing - you have no control," and it's clear that on one level he's talking to the likes of Ahmet Ertegun who would later offer the band a deal with Atlantic and invite them to name their own terms, you also sense that there is as much about that sentiment that applies to the band's audience, too. The relationship was famously fractious: pick more or less any two or three gigs at random from the utterly wonderful Fugazi Live Series - an online archive of recordings of more or less every gig the band have ever played, downloadable for a suggested price of $5 each - and chances are you'll find one where the set is punctuated by MacKaye and Picciotto remonstrating with a hostile crowd. Why you'd turn up to heckle a band remains something of a mystery to me: less difficult to grasp is why some audience members would wish to respond to this music with stage-dives and slam-dancing, though it's by no means easy to understand why people would persist in doing this once the musicians had politely asked them to stop, and explained that this was to ensure people didn't get injured.

Yet perhaps what comes through loudest and strongest from Repeater is the way they record addresses how the personal becomes the political - which is in itself almost, in a way, a description of what Fugazi as a band ultimately have come to represent. The title track, an intentional play on The Beatles' Revolver, is an overt means of addressing DC's then spiralling gun problem, but becomes a meditation on how a yearning for some kind of personal pre-eminence ends up with the risk-taker becoming part of a background of nameless statistics. 'Shut The Door' is clearly about an overdose victim, the music effortlessly well suited to highlighting the drama and the emotions, but the lyrical point of view switches between MacKaye's witness to the unfolding tragedy crying desperately for help that cannot come, and that same individual describing their quest for freedom that turns into addiction, and which consumes both body and soul: "I burn a fire to stay cool/I burn myself, I am the fuel." And in the magnificent 'Styrofoam', the way in which personal poisons can contaminate society is conflated with how toxic waste destroys the environment. It's magisterial writing, a polemic made more powerful by its openness, its success achieved because its makers were willing to risk being misunderstood. There are lessons here we can all learn from, if we're willing to listen with an open mind.

Fugazi remain, at least notionally, a band. They've been on hiatus since the last of three gigs at the Forum in London in November 2002, and despite occasional rumours of a megabucks festival show, the members have periodically reaffirmed that the only thing that will get them working on new music together will be a combined belief that they can outdo their best work, and that the other personal factors that have contributed to keeping them away from one another - Lally now lives in Italy - will be aligned in a way as to permit them the focus that being a heavily drilled, extensively well-rehearsed outfit requires. This feels somehow fitting. Their influence remains detectable across a wide swath of the musical landscape, and their records sound so immediate that Fugazi, more than the vast majority of lauded bands, feel like they're a constant part of the present, not a monument to the past. MacKaye continues to add tapes to the Live Series, so there's always something "new" to become absorbed by. They never broke up, just like they never sold out: and they remain the one band you feel sure will never let you down.