The atmosphere in Finsbury Park is so charged that it feels as though it's heralding an oncoming storm. The excitement is so palpable as to feel like a giant physical presence willed into existence by the 45,000 strong crowd that's made the pilgrimage to north London, to witness the second leg of what can be considered the third coming of The Stone Roses. Glancing around the crowd is to witness a congregation that so few other bands can attract; those who were there for the band's late 80s/early 90s heyday, their offspring, those about to witness the band for the first time, an almost equal split between the sexes, kids born not just after the band's demise, but those of their musical descendants too. To a person the desire is the same: for this reformed quartet to take the stage and give them the release they so desperately desire.

Taking the stage to the apt strains of The Supremes' 'Stoned Love' – "A love for each other / Will bring fighting to an end / Forgiving one another…" – the reunited Ian Brown, John Squire, Mani and Reni are met with a delirious release of energy. Even before a note has been played, the devotion on show here is at the level that religious leaders hope, yet so often fail, to achieve. A few shared glances between the principal players, Mani's rumbling bass ushers in 'I Wanna Be Adored', and the overwhelming feeling is that of standing in the middle of a massive, collective orgasm.

So why The Stone Roses? Why then and why now?

Though much pop and rock is a matter of contrivance, there were, are and will be those unlegislated moments in pop culture where music, fashion, youth, location and drugs meet and align for a period of time where life feels that it's achieving all of its utopian potential. This is a time and place where, through a shared love of music, dancing and the joy of life, the horrors that the outside world can and do throw at you are left behind at the door. Call it naivety, call it the optimism of youth, but once experienced, that feeling is a goal to be strived toward and, however fleetingly, to be achieved and held onto until the next time.

When The Stone Roses broke through, firstly on a local and then a national level, they offered a form of inclusiveness hadn't been prevalent before. With most rock gigs of the 80s, the chances were that you'd be returning home with, at best, bruises on your body or, at worst, a boot mark stamped on the side of your face. This was something else: a breaking down of barriers to create a party where everybody was invited. And crucially, as the soundtrack to that party, it's essential to understand that The Stone Roses had, and still possess in abundance, The Funk. This wasn't music to mosh or slam to. Nor was it, worse still, about standing around looking awkwardly at your shoes, and swaying from side to side like someone suffering the after-effects of a traumatic event, while a bunch of equally awkward-looking pale white kids knocked out bloodless music. Not since the days of Gang of Four or Orange Juice did a rock band owe so much of its sound to black origins.

Now, just as back then, the country is being squeezed by a heartless administration intent upon pursuing policies that cause as much hurt, upset and misery as can be heaped upon those who least deserve it. It's at times like these that a release is needed, and what we have here tonight, on the second of The Stone Roses' gigs at Finsbury Park, is a communion of dance.

To understand the appeal of The Stone Roses in a live context, the best approach to take is to look at this as not so much a gig – which, technically, it is – but as a gigantic party. This is what pretty much sets them apart because, along with wanting to sing at the top of their lungs, the masses that have flocked to this pocket of London are here to dance. Sure, you get a few beery types stumbling around with all the grace of an elephant in a tar pit, but for the most part people afford each other a surprising amount of space to groove, frug and shake their tails in bug-eyed wonder – and that's even near the front, where The Quietus finds itself located.

As the band launch into 'Elephant Stone', it remains abundantly clear that, in Mani and Reni, The Stone Roses possess the funkiest rock rhythm section since John Paul Jones and John Bonham. Yet unlike the hard-hitting Bonzo, Reni's infectious beats are characterised by a lightness of touch and a sense of swing that eludes so many tubthumpers. As John Squire's chiming notes nod an acknowledgement to Roger McGuinn and Mani's bass underpins the bottom end, the rhythms at the back of the stage are the thing that cut through the most, as they make their way from the ears to the feet to do their do.

As with most parties there's always going to be a lull - usually at that point when someone cries out "I've got something I want to play", and so triggers an exodus to the bathroom, kitchen or outside for a quick fag. And, surprisingly, the dip occurs during the second of half of 'Fool's Gold'. Though widely regarded as one of the finest guitarists of his generation, Squire – on tonight's evidence – doesn't have quite enough ideas to stretch the track out into anything more than a pleasant enough jam, and things take a dip as the band move into a soporific 'Something's Burning'. As they noodle on, conversation levels increase in the crowd, dancing decreases and the run to the bar and toilets becomes evident, as streams from the throng snake their way through to their destination. There's irony here, too: the moment The Stone Roses consciously funk out they sound like a rock band, yet once they go back to playing rock they become funkier.

Squire is at his best and most focussed when taking the path of least resistance, as evidenced by a devastating 'Waterfall' - here The Stone Roses not only hit the spot, they rub the fucker out. With his hair cascading over his shoulders, the guitarist's fluid playing is astonishing, as notes shimmer, dance and flow like liquid gold. Mani's bass fills in the gaps, swooping, turning and then flying back in again. On the flip of a coin, the party is back on again: arms are waved in the air, feet begin to move and those voices are raised to the heavens.

And what of Ian Brown and his infamously unreliable voice? For the most part he strikes his targets well, but on those occasions where it hits the buffers – 'Don't Stop' and 'Breaking Into Heaven' would, with a little Grand Marnier and marmalade, make a delightful treat on Shrove Tuesday – he's helped along by the dedicated masses, who take his part and aid him to his destination. It's all a bit like the end of Rolf Harris' 'Two Little Boys' brought delightfully to life in an urban park rather than a bloody battlefield. But here's the thing – this is one of those rare occasions where the audience are as much a part of the band as the four Mancunians up on stage, and they're only too happy to pick up the slack from Brown as and when necessary. So, does he hit the notes during an ecstatic 'This Is The One'? Who knows, and who cares anyway? Because the sight of a crowd this size singing as one, arms aloft or wrapped around each other whilst dancing with unselfconscious abandon, is hypnotic and seductive.

The climactic 'I Am The Resurrection' feels like a reward to all present, a 'thank you' for the singing, the dancing and the participation. The choruses are nearly drowned out by the thousands of voices that take the lead, and the final coda sees Mani and Reni lock into a murderous groove as John Squire takes flight with some truly astonishing guitar work that alternates from light licks to heavy fretting. Ian Brown, meanwhile, has left the stage to press the flesh of the faithful.

And so it ends, for now, with a group hug that leaves their constituency breathless, smiling and elated. There are many here hoping that the next time they hit the road it'll be on the back of new material. The band have already acknowledged that they're working on new stuff, but whether the wait for it will be five years or more, the certainty is that this gig will have increased the appetite for it. Until then, we'll always have now.