Beirut, Roundhouse, London

Watching Beirut in a venue so packed that, despite being huge, there is no room to dance, it is hard not to wonder how many of the people here share frontman Zach Condon's love for European, near-eastern and Gypsy music, and how many require the filtering of an American imagination/indie-rock sensibility to appreciate it.

When Condon burbles excitedly of how he recently met Macedonia's Kocani Orkestar, before launching into a playful rendition of that band's Siki Siki Baba, hardly anyone seems to know what he is talking about. Maybe they just can't hear: most of his between-song chit-chat is garbled by the oddly balanced sound system, which is besotted with trumpets and careless of all else.

Questions of authenticity and cultural appropriation have dogged Condon since he released his debut album, Gulag Orkestar, last year, spurred in part by the weird, suspect disingenuousness of his band name and that album title. In a sense, Condon is just another youngster (he is now 21) who has travelled around Europe and returned home with a head full of naive ideas and a suitcase full of mandolins and CDs picked up in flea markets. What sets him apart is the passion with which he learned to play like the bands he encountered, and his own talent.

Where once it was Condon's bedroom project, now Beirut really is an orkestar - of people whose aptitude on a myriad of instruments is as impressive as Condon's own. There is a velvety richness to every song, and such variety of melody it is impossible to track all of them. That's partly down to the venue's soupy sound, which blunts the mandolin and ukulele strings, swallows the double bass and reduces every drumline to a throbbing heartbeat, and partly Condon's choice. As with Kocani Orkestar, the wind instruments are the vivid, garrulous focal point.

What grabs the audience, however (and probably what makes people listen to him, rather than his influences) is Condon's voice. It is sonorous and full-blooded, reminiscent of Morrissey and the Magnetic Fields, operatic in its range and meticulous enunciation: rarely can the letter "T" have rung this truly on a rock stage. Most importantly, it's so rousing, you cannot help but want to sing along, as seemingly the entire crowd does on Elephant Gun - the moment when all questions about Beirut are drowned in sheer joy.