Glasvegas, Reading FestivalLast Shadow Puppets, Reading Festival

Alex Turner may be bidding for the Mercury Prize, but all eyes are on Glasvegas as the most important breakthrough band of the year

It's amazing how loud you can sing when you've got a lump in your throat. If Glasvegas are the most important British breakthrough band of this year, just as MGMT are the most important from America – and the only doubt about that is whether we're talking merely this year, or years – then traditional values of rock'n'roll cool have little to do with it.

Oh, in one sense, Glasvegas totally look like a classic band. Dressed uniformly in black, with (on the male members, at least) proto-Eraserhead quiffs. And in another sense, they don't look like a band at all. The top of drummer Caroline McKay's head doesn't even come up to the shoulder of giant bassist Rab Allan (singer James Allan's cousin). And while their ages are hard to estimate, it's fair to surmise that a couple of members have a little more life-experience under their belts than the other two.

Something about this Spectoresque Scottish quartet has connected with the hearts of everyone who hears them, and the tent at the Reading Festival is crammed with everyone from sensitive souls to lairy lads, craning their necks to catch a glimpse of their new heroes. The primary reason, I'm certain, is their naked emotionalism.

Part of it is simply the voice. There's a catch in James Allan's singing which brings tears to the eyes, a sincerity which is somehow amplified by his admirably stubborn refusal to sing in anything other than his natural Glaswegian accent. And Scottish pride seems to surround them. There are three flags flying in the crowd: two saltires, and one cross of George.

With a voice like that, following melodies you swear you've heard somewhere before in some half-imagined pop classic from the early seventies or the late sixties, and swollen by a sonic tsunami which recalls the golden age of The Jesus And Mary Chain and My Bloody Valentine, Allan could be singing a verse from a Hallmark greetings card and it would still get to you.

What takes Glasvegas to another level, though, are lyrics which bear a true-life, kitchen-sink-drama authenticity of a kind we've heard only fleetingly (Pulp in their more serious moments, perhaps) since The Smiths. He may be hiding behind wraparound sunglasses tonight, but it's the only sense in which James Allan is hiding anything at all. In his words, he reveals so much.

They open, tonight, with "Flowers And Football Tops", which deals with the aftermath of a sectarian or racist murder, and segues into a ghostly rendition of the trad-jazz standard "You Are My Sunshine".

Their set continues with the deeply-ironic rabble rouser "Go Square Go", which is actually about the brutality of teenage fistfights, and "Geraldine", a hymn to a guardian angel social worker (whose real-life inspiration is now a full-time member of the Glasvegas retinue).

"It's My Own Cheating Heart That Makes Me Cry" is an incredibly honest and excoriating expression of the crippling, self-defeating guilt of the love-cheat. Tonight it's dedicated to a fan who has had the words tattooed onto his arm.

They end, as always, with the tearjerking "Daddy's Gone", a song about absentee parents from the point of view of an abandoned child which lashes out at the missing father: "I won't be the lonely one, sitting on my own and sad/A fifty year old, reminiscing what I had..."

James leans away from the mic to allow the crowd to take one line. A corny old showbiz trick, but it rapidly runs away from his control, takes on a life of its own and turns into something truly extraordinary as the throng takes on the whole chorus at top volume. He looks taken aback, and stands against Caroline's drumkit, watching in astonishment, when they take another. Long after the band have kicked back in with the grand finale and walked offstage, one entire corner of a Berkshire field continues to echo: "He's gone, he's gone, he's gone, he's gone, whoah-oh..."

Over in the other corner, something more formal is taking place as The Last Shadow Puppets put as much space as possible between Alex Turner's latest project and The Arctic Monkeys' slouching diffidence.

There's a courteousness about the Last Shadow Puppets, from Turner and sidekick Miles Kane's suited-and-booted dress code (a change from the Monkeys' worn-out jeans scruffiness). Their guitars are worn high on the body, as though they're making their debut on Ready, Steady Go, and they're backed by a full 16-piece orchestra.

The Last Shadow Puppets are a dark chocolate pleasure, whereas The Arctic Monkeys are beer'n'chips. There are plenty of people who reach for the sickbag when they hear the latter, but can listen to the former all day long. What the duo have done, on their Mercury-nominated album, The Art Of The Understatement, produced by James Ford of Simian Mobile Disco (who drums with them tonight), is to tap into the sweeping romanticism of a certain strain of late Sixties psych-pop: Scott Walker and Love being the most-cited names, but one could also mention Paul & Barry Ryan, and David McWilliams.

In theory, it's an equal partnership, a balanced supergroup, even if The Rascals' (Kane's band) debut album only reached No.100 in the charts while the Monkeys sell by the million. Onstage, the lead vocal duties are shared equally although when Turner makes an announcement, there are screams.

When the Mercury award ceremony comes around, any result other than a British Sea Power victory would be a travesty. But as travesties go, a second win for Alex Turner wouldn't be too hard to swallow.

Need to know

Singer James Allan pursued a career as a professional footballer, playing as a left-sided midfielder for clubs including Cowdenbeath, East Fife, Queens Park, Stirling Albion and Dumbarton, scoring 9 goals in 105 matches, before forming Glasvegas in 2006. A CD of demo versions, 'The Home Tapes', was circulated free at gigs and in 2007 their first limited-edition single, 'Go Square Go', was released. They won the Philip Hall Radar Award for new bands at the 2008 NME Awards and signed to Columbia earlier this year. Their self-titled debut album is out next week. This will be followed later this year by a special Christmas album recorded in Transylvania.