Frank Gehry, infamously, doesn’t like to explain his buildings. He likes the spaces to do the talking. So what’s his Serpentine Pavilion, the ninth in the gallery’s series of temporary architectural installations, saying?

To many it will say cacophony. The old adage of architecture as frozen music is especially appropriate for Gehry whose work, if anything, is about introducing a new, polyphonic rhythm to architectural order. The Canadian architect is a hands-on guy, eschewing computers for model-making, desperate for something of the directness of music to make it through the box-ticking of the average building process. His baggy geometry is more about improvising with your buddies in the garage than intellectualising - but there is order beneath the seeming maelstrom.

Approach the pavilion and all seems chaos, the casualness of Los Angeles, Gehry’s adopted home, juxtaposed with the English neo-classical formality of the Serpentine Gallery building beside it. Two giant arches, steel at the corebut clad in massive Douglas fir timbers, appear to have tumbled together, their junctions random. The roof’s glass and steel panels tilt this way and that but never meet, thrown about like leaves in an eddy. Glueing the entire structure are white-painted beams. Who made this mess?

Yet the rhythm is mostly glorious, its shambolicism rigorously held together by its simple, formal axis - a street, framing the gallery, with seats on each side. You might not like the noise; but at least admire the skill.

Gehry never fitted the Bilbao Guggenheim stereotype into which he was shoehorned. He soon returned to his 1970s roots, serendipitously inventing a DIY aesthetic at odds with the arch-formality of the “deconstructivists” such as Zaha Hadid and Daniel Libeskind with whom he had been pigeonholed.

This pavilion is the real Gehry: chunky, clumsy, jagged, direct.

It is at its unintentionally clunkiest beneath the roof, where the demands of health and safety and cupboards for cups - the pavilion will house a café, and act as a venue for film screenings and talks - interrupt the music with a clatter. He dumbs down poorly. No wonder all he’s built before in the bureaucratic UK is the tiny Maggie’s cancer centre in Dundee.

With the economy as it is, and Gehry in his late seventies with, he hints, only a couple of years of design left in him, you can kiss goodbye to any more performances by him on these shores. But as a booby prize, this little tune is pretty darn good.

From 20 July to October 19 www.serpentinegallery.org

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