It's the encore on the first night of the Black Keys' sold-out trio of dates at Alexandra Palace. Outside, wet flakes twinkle in the streetlamp glare. Inside, the room is lit by a giant mirrorball, a prop whose power to make everything look magical resists logic. Not unlike the Black Keys themselves – a band who really shouldn't be this enjoyable.
The song playing is "Everlasting Light", a tender boogie from the Black Keys' hit album, Brothers. Guitarist Dan Auerbach is singing in a supple falsetto, asking a girl to trust him in words that, re-scored, might belong to a hymn. It's one of his more beguiling performances, given that Auerbach is not normally the sort of lyricist you look to for scintillating epigrams. His songs have tended to stick to classic blues-worthy themes without noticeable flair.
Drummer Patrick Carney – a gangly hipster caveman blessed with the funk – is the band's secret weapon. His grimacing dyspraxia results in some of the most elastic and hard-hitting drumbeats in rock. Right now, though, he is becalmed, tapping gracefully at his kit rather than trying to demolish it. The two have spent most of their set going hell for leather through a catalogue in which a hoary old blues-rock skilfully acquires a 21st-century pop sheen. "Little Black Submarines", earlier in the set, starts with Auerbach imploring a telephone operator as "Stairway To Heaven" by Led Zeppelin is invoked beneath. Then it locks into a hairy groove that somehow manages to sound like a pop song.
Falsettos, mirrorballs and pop success are not the sort of thing one used to associate with the Keys, who emerged out of Akron, Ohio in the early 2000s. They had the misfortune to share a set-up (guitars, drums), an ascetic sound (attitudinal blues-rock) and a name involving a colour with another band of the time, the White Stripes. A third of the way through tonight's set, the Black Keys revert to being this very two-piece, pranging and crashing joyfully through old songs like "Thickfreakness" and "Your Touch", going mano a mano, guitar versus drums.
It is a marker of their dogged self-belief that, despite being perceived as inferior copyists, the Keys kept plugging away, refining their sound. Bass and keyboards crept into the set-up around the time of 2008's Attack and Release, paving the way for the Keys' genuinely soulful hit album, Brothers (2010). This brought some much-needed depth. At one point before its recording, Auerbach and Carney weren't speaking. While Carney was in the throes of a messy divorce (anyone dating a musician should consult Carney's ex-wife's take on their break-up on Salon.com), Auerbach made a solo album, which Carney took badly. The two were eventually reconciled and at last had some blues of their own, rather than those recycled from old vinyl. "Next Girl" ("won't be nothin' like my ex-girl,") two songs in, remains a piquant reminder of that album's hard-won thrills.
With three Grammys and nearly a million copies sold of Brothers, the Black Keys are now touring much larger venues than the White Stripes ever did, at a time when guitar bands are not supposed to be this popular. They sold out New York's Madison Square Garden in 15 minutes. That should make things awkward in the guitar shops of Nashville, where the Black Keys now live alongside Jack White (whose song "Machine Gun Silhouette", incidentally, leaked this week).
Tonight's 21-song bop through the catalogue is the very definition of success. Their taut, crunchy songs have all the hallmarks of good pop music – deadly hooks, nagging choruses, irresistible momentum – coupled with the signifiers of authenticity – rootsiness, effects pedals, beards – that rock fans require. And if you occasionally find yourself wondering what, exactly, is the difference between some of the Black Keys' songs and some of Lenny Kravitz's, it's not in a disparaging way. It's a genuine benchmark of how wide an audience this band have now reached.
The almost comically rocking El Camino is faster, pithier and more mercenary in its riffage than Brothers, and the Keys dose it out carefully throughout their set. They end with "Lonely Boy", which sounds even better live than it did as a single. Auerbach announces, with typical understatement, that El Camino has just gone gold, "so this is kind of a celebration". They will never be a band whose gigs can irrevocably change you inside, but the Black Keys are a lot of fun. Even the man doing the monitor mix, you notice, dances through every song.
