Coldplay, iTunes Festival, Roundhouse, London

"You have to jump to this," Chris Martin commands before "Viva La Vida". Only it's not really a jumping song, they're not really a jumping band. Although the rangy Martin, bless him, regularly bounces on the spot like a welterweight.

For this free event the indie four-piece are armed with a generous amount of gimmicky pyrotechnics and bombast – the Back to the Future theme announces their arrival, there's a fluorescent light show towards the finale, giant balloons are everywhere and pretty multi-coloured paper is fired from a cannon. Coldplay are a pretty polished and slick act these days. In fact, there's something a bit Vegas about Martin and his outfit. These are not gnarled individuals or twisted souls. They don't do politics, although one of their best songs and a highlight tonight is "Politik". They're not perverse, kinky or strange. And strange, in pop, is good. Their sound is calculating and stadium-friendly. There's little menace, spite or soul about them. And you can't dance to their solemn anthems. Sway possibly, raise your arm maybe. But it barely matters when Martin can bang out so many gorgeous pop melodies, the likes of "Fix You" and "Yellow".

Unfortunately, this freebie (As Martin jokes: "Twelve years ago we played up the road and had to give away all our tickets, turns out nothing's changed") in front of competition winners, well-heeled hipsters and celebs (Noel Gallagher and Jamie Oliver are here) is plagued by constant hubbub and chatter. "Everybody okay so far?" enquires a sweaty, slightly flustered Martin in a transatlantic twang. You almost feel sorry for this millionaire, with his Hollywood actress wife and hip-hop superstar pals (Jay-Z), as a section of the crowd don't feel engaged at such an intimate gig. Only on the rockier numbers, the Radiohead-like "Shiver" and "Violet Hill" in particular, where Coldplay look happiest, especially the imposing guitarist Jonny Buckland and ace drummer Will Champion, do the band manage to drown out the dinner-party hubbub. New songs, like the drone-heavy "Moving to Mars" and "Charlie Brown", are lost under the blather.

However, they end impressively with the emotive "Clocks", the lovely "Fix You" and the new release, "Every Teardrop is a Waterfall", their Big Country-style stomp. For all their effort, and Martin's swagger and strong vocals, this wasn't as stirring as it could have been. It feels a tad flat.