The Specials, Academy, NewcastleP J Harvey, Shepherd's Bush Empire, London

Even with founder Jerry Dammers missing, the 30-year-old Specials are on fantastic form

There are records you never forget hearing for the first time. There are records that change your life. For me, "Gangsters" by The Special AKA, later to become known as The Specials, was both.

In an instant, punk was deader than dead, no more than a yellowing copy of "Pretty Vacant" in a charity shop window and cheap day-glo socks on the high street. A stark, bracing monochrome aesthetic, at once vintage and fresh, had swept all that away.

2 Tone Records – the label that launched them, along with a rapid succession of bands including Madness and The Selecter – changed the way you wore your hair (a buzz-cut as short as you dared without getting expelled from school), the way you dressed, the way you danced (an explosion of knees and elbows) and, crucially, the way you thought.

2 Tone caught the mood of a nation in a time characterised by unemployment, police brutality, urban decay, racist violence, and the spectre of atomic Armageddon. So, when they play their first concert in 28 years, why do I feel such conflicting emotions? The reason is the gap-toothed ghost at the party: keyboardist Jerry Dammers, the genius who recruited every member and wrote most of the songs, who has been frozen out of this reunion – or, as he prefers, "takeover" – amid much public bickering and bitterness.

But if there are any dissenting voices chanting "Jerry, Jerry!" tonight – and there's a faint one inside my head – they're drowned out by a jubilant chant of "Rude Boys, Rude Boys!". The atmosphere is astonishing, hundreds of hefty skinheads amiably chanting Jamaican ska tunes (the 2 Tone message of peace and harmony clearly rubbed off), and when the curtain parts and a brutal tattoo announces "Do The Dog", the Academy erupts.

The Specials – six-sevenths of them, anyway – rattle through early classics like "New Era", "Rat Race" and "Gangsters" at such full-pelt velocity that the relative torpor of "Blank Expression" becomes medically necessary.

Age may have withered them somewhat, but their energy levels have barely diminished. The hollow-eyed Terry Hall is the only point of stasis, exuding, as ever, aggressive boredom in contrast to his manic sidekicks Neville Staples and Lynval Golding. Apart, that is, from the funny little curtsey he does at the end of "Rat Race" (Hall even has sarcastic body language).

For the first eight songs, there's nothing from More Specials, Jerry Dammers' muzak-inspired masterpiece and the record where the band's eventually fatal musical differences were most audible. Then something extraordinary happens. A flourish of mariachi trumpet, and we're into "Stereotype", the arabesque tale of a beer boy's drink-driving death. All seven minutes of it. Next, Neville Staples yells "waarnin', waarnin', nuclear attack!" and the band lurch into the dread-filled dub of "Man At C&A". He may not be here to hear it, but his former bandmates have done Dammers proud.

Many of the 30-year-old songs are eerily relevant. The dejected, resigned reggae of "Do Nothing" might have been written in response to the G20 protests, and the anti-racist anthem "Doesn't Make It Alright" echoes around my mind the next day – St George's – when I see a neo-Nazi rally at Grey's Monument. We need a band like The Specials as much as ever.

After they've ended with the eerily prophetic "Ghost Town" and encored with the brilliantly obnoxious "Too Much Too Young", the singer says it's been a privilege to play for us. Then something even more extraordinary happens: Terry Hall smiles.

You don't go to a PJ Harvey concert expecting laughs, such is the aura of intense solemnity surrounding everything she does, to the extent that even when she dabbles in colour, it's deconstructed: "Ah, so that lipstick and leotard is a clever parody of female foxiness. (Hazardous, of course, to mention foxes near pop's biggest bloodsports enthusiast this side of Bryan Ferry.) In reality her reunion with John Parish, respected arranger for the likes of Sparklehorse, Goldfrapp and Eels and Harvey's on-off collaborator since her pre-fame days, is more fun than it looks on paper.

Polly's looking splendid in a pearl-studded vintage dress, high-swept quiff and a chain seemingly made from recycled cans hanging from her head, while Parish, hunched over a guitar, banjo or ukelele, hides beneath his trilby. Together they revisit 1996's excellent Dance Hall At Louse Point and this year's A Woman A Man Walked By.

It has its moments, from the killer riff to "Black Hearted Love" to the strange bellow she adopts on "The Crow Knows Where All The Little Children Go", but most surprising of all, there's at least one laugh-out-loud bit. It's the part in "Pig Will Not" where Polly, quite unexpectedly, begins to bark like a dog. With the echo in the Empire auditorium, it could almost be mistaken for a pack of baying beagles. Tally ho ...