"Same three guys," says Billy F Gibbons, pondering ZZ Top's 45 years together. "Same three chords." And, yes, you don't have to be a boogie sceptic to point out that there is, at times, a similarity between some of tonight's songs, no matter what point in the Texan trio's history they come from – Chartreuse, from last year's comeback album, La Futura, bears a striking resemblance to the final encore, Tush, from 1975.

But, equally, it's self-deprecation, for ZZ Top are a long way from being a generic blues band. The show itself is something of a marvel, introduced on big screens like a movie – certified ZZ, of course – and closing with a full credits list, running through not just the band but their crew, too. Smaller screens in front of the amps flash "Basic amplifiers" between songs, testimony to Gibbons's humour – both bone-dry and utterly absurdist.

The setlist, too, highlights the variety that can be wrung from 12 bars of basic chord progressions. Last year's extraordinary single I Gotsta Get Paid takes a Houston rap song about dealing crack, bolts on a Howlin' Wolf-inspired guitar line, and showcases Gibbons's playing and singing at its most toxic: both instrument and voice sound like they've been immersed in chemical soup. Legs – from 1983's smash album, Eliminator – adds a sequenced disco pulse to the rock'n'roll, and sees Gibbons and bassist Dusty Hill donning square, fur-covered instruments.

Hill calls the ZZ Top show "low movement, high impact", and that's as good a description as any. The two biblically bearded frontmen restrict their stage moves to the occasional synchronised half-stroll to the mics, save for Waitin' for the Bus, when they add a half-turn and tip of the guitars as they sing the "Have mercy" refrain. So distinctive are they, so beyond parody, that it's more like watching some exotic, endangered wildlife than a rock band.

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