"I knew something was up when I came in through the door. You were in tears and my shit was all over the floor..."

Put me in it man. Take me there.

Mexico City do bad love good. With their big Crazy Horse guitars and a Neil Young stagger to their melodies, an instant sonic stride that pulls me towards them straight away. By the time they are playing "a new song" they're making me feel this thing, imagistic, out there, like my legs are made of electricity and I'm thirty feet tall, walking down a country road or a city street, it doesn't matter, one hand pulling at the sky, feeling happy, angry, sad, feeling feelings, feet of pride leaving traces behind me and warning of my coming too. What a sound it is. Complicated at heart, direct in tone, deep as a wave.

Mexico City are: one intensely committed drummer full of thrash and plunge, a la Keith Moon and Crow's Johnny Fenton (yeah, a real rhythm freak to the max); bass and two guitars moving in a duel one minute, then like the floor of a drunken bar the next; with just a faint touch of Bad Seeds lunge to it all. And a voice out front that's deep inside itself somehow, a half-way-down-a-bottle croon, shouting nasal-sweet and romantic, as if the guy's caught inside his own head and these lyrics are just the map we're hearing of things he is so much closer to than us, things he's still living and breathing in some unfinished way. It's so intimate it seizes you.

Mexico City. There's some kind of greatness in their bones. If they can operate with just a little more of the joy that Kings of Leon have tapped, the world might well be theirs.

They make it tough for The Black Keys to follow on. Much as the entire pub are busting to hear them blow the roof off as they start note-perfect and surging on Thickfreakness then Set You Free - with a dense, driving sound that comes over like it's being thrown against the sky, Hendrix style.

Is that it, I begin to wonder: a whole night about the sky?

As earthy as both bands may be this evening, there's a definite lift to the sounds on display and to the whole rock 'n' roll revival that's going off everywhere round this planet. The Black Keys do it by pulling on the coarse sinews that lie between Hendrix and the Chicago electric blues masters. As Fat Possum recording artists they also display more than a passing debt to dirty-ass genius of this era, R.L. Burnside. If The Black Keys don't quite match Burnside's erotic, good times slither and chug, they certainly churn out a mighty sound for two little white American guys on a tiny Australian stage.

Drummer Patrick Carney and singer-guitarist Dan Auerbach are incredibly strong, and when I take a quick break for a too-early piss I can hear them coming like thunder through three large rooms and many more brick walls. They're so strong I find myself wondering how they might unpick their sound and make it just a little less fat and tight and full, and thereby make space for something else: a little more lyrical availability beyond Auerbach's sweet, smudged slur of a voice; a thinner line of guitar; even the sacrilege of a third instrument on a song or two (in my mind I hear a wild, scrappy honky-tonk piano jarring its way into things).

As Carney is beating his cymbals with a tambourine and punishing his bass drum while Auerbach wails and moans and rips amazing cross-town traffic from his guitar, however, it seems uptight to complain. The Black Keys are a very fine band indeed. And they do sound just like their mighty record does. Which is maybe why I feel vaguely disappointed at the absence of something more (or less) - at the lack of surprise in encountering them live.

It's clear The Black Keys are flowing with the current of their own hot-voltage ecstasies to try and get on to that higher stream you can hear just ahead of them. A sound that suggests so much more sex and love and sweat and glory than is finally here this evening. Instead tonight is only really good. I'm sure they have that bigger ability in them - that on their night, when they stand up next to a mountain they can chop it down with the edge of their hand. In the longer run the dilemma for them will be not how to cut a mountain down with that powerful sound of theirs, but how to float right over it.