The dreadlocks are gone, the dark suit is gone, the acoustic guitar which was his faithful travelling companion during the four years as Brazilian Minister of Culture, is also gone. Instead, Gilberto Gil skipped on stage with a cool, short, grey haircut framing his beautifully sculpted features, wearing a white shirt and check trousers, and strapped on a Fender Stratocaster.

So little time, so much stuff to see: that, in essence, is the story of Latitude. Now in its fifth year, this Suffolk festival offers a bewildering cultural cornucopia: music, theatre, dance, cabaret, comedy, circus, literature, poetry, as well as unexpected oddities such as performers dressed as unicorns wandering the woods at night and teams of ghoulish “medics” defibrillating random victims (I was one of them) during theatre group Duckie’s Saturday night masked ball. It’s a blast (albeit one that is almost entirely white and middle class - a state of affairs that has led to it being dubbed “Lattetude”). And it was made especially lovely this year by the weather gods, who delivered a couple of brief bursts of rain but otherwise blessed the event with clear warm dry days.

Was this a Corinne Bailey Rae audience or a Somerset House audience? “We’re Somerset House fans,” I heard one posh punter proudly tell some friends. Then later I heard a woman talking about the Florence and the Machine gig that she’d missed earlier in this short season of concerts, as if it were a stamp missing from her collection. Could this really be an audience who were here for the building first and the music second? Yes, this enclosed yet open-air square in central London is a delightful space, but when did ambience become more important than music? And anyway, there’s no space on Earth that could make Florence and the Machine sound good to me. But Corinne Bailey Rae, now that’s a different matter.

Laura Moody says she was given a cello as a child to curb hyperactivity, but listening to her last night you might well have wondered if she’d had Tourettes too. The singer-cellist’s sound included clicks, shrieks, howls, and a lot of things that probably shouldn’t happen to a cello - as if she had taken every musical influence that had come her way in her 28 years and put them in a blender. The result? It was certainly extraordinary and sometimes disturbing. What surprised me most, though, as I sweated it out in a muggy hall was just how often it became mesmerising.

I don't know exactly what they do in the music classes at Putney’s Elliott School, but it seems to do the trick. Fleetwood Mac's Peter Green went there 50 years ago and now, after admittedly a bit of a lull, the school is positively spitting stars out by the vanload. Kieran Hebden, aka Four Tet, attended, Hot Chip's members are Elliott alumni and The xx are the latest schoolkids on the block, with their self-titled 2009 debut album tipped to be a serious Mercury Prize contender.

Onstage last night, however, the Twilight-style black-garbed trio of vocalist/ bassist Oliver Sim, percussionist Jamie Smith and vocalist/ guitarist Romy Madley Croft revealed the band's limitations as well as their strengths as they studiously worked their way through most of their only long player. There is a fragile beauty to the songs when played at home, but in the flesh most of their material starts to sound a little bit, well, samey. At its best it is timeless minimalist pop, pared down to its bare bones, Chris Isaak meets Philip Glass, as on "Crystalised". But elsewhere there is too much of The Cure and New Order at their gothiest gloomiest. And the simplicity is not always sophisticated. "Heart Skipped a Beat", with its childlike hook, keeps threatening to turn into "Three Blind Mice".

It is never a good sign when one is making notes at a gig and one finds oneself writing, "Must call dentist tomorrow about daughter's teeth." Despite, or maybe because of, the glorious white-walled architectural setting of Somerset House, there were just too many distractions unless you really, as Howard Devoto said in a different context, wormed your way into the heart of the crowd. On the fringes there were those triple threats of the modern live concert, people taking photos of each other, people so excited by the gig they had to ignore it and text their friends to tell them how excited they were, and people nipping off to the bar. Though regarding the latter sin, in mitigation the bar was undeniably appealing, due to the venue organising a speedy and fair queuing system very similar to the one in my local post office. Not that they serve Carling on tap at my local post office.

The still relatively rare sight of a woman on lead guitar is more refreshing than any cold lager, but Madley Croft does little to add to the recorded versions of their songs. Sim is a lithe, lively bassist, bobbing and weaving around the stage as if ducking imaginary missiles, but his banter is largely limited to talking about the "funky house" before the band's positively glacial cover of R&B chanteuse Kyla's "Do You Mind". Only a few tracks really stood the test of live performance. "VCR" – a song title The Human League would surely use if they were starting out today – had a beefed up feel compared to the frankly plinky plonk version on their album and "Islands" retained its itchy, infectious vibe thanks to a nagging riff and Madley Croft’s whispered vocals cross-cutting with Sim’s drawl.

Frustratingly though, the threesome never quite built up more than a functional head of steam. At Glastonbury recently they were joined onstage by Florence Welch minus her Machine for a radical unpicking of "You’ve Got The Love". It would have been a wonderful way to finish with a flourish last night. Instead we got sparkly glitter shot out over the audience and a recorded version of "You’ve Got The Love" as everyone headed for the bus. If any Elliott School music teachers were present I hope they gave their ex-pupils good marks for effort but less plaudits for charisma.

Overleaf: watch The xx perform with Florence Welch