A jam-packed month of giant stars playing relatively intimate gigs in Camden’s Roundhouse is coming to a close. Confetti of various colours and shapes can be found wedged into cracks that can’t be swept, having accumulated over the last 29 days. What’s refreshing is that an Apple sponsored event actually has relatively little Apple branding once inside the venue. There’s only a banner up for a few minutes with a hashtag, and Katy Perry weirdly refering to the crowd as “iTunes” a few times. Yeah, someone should explain what iTunes is to her and why it’s odd to talk to a group of people as if they are a brand of music software.

Icona Pop take the stage in colour co-ordinated black and white dresses as a House-y intro blares out. There’s a giant chunk of glass, that looks like something out of The Crystal Maze, which houses their decks and laptops. The ladies pump out enthusiasm, and even bring what looks to be a kazoo into their set. Their big hit ‘I Don’t Care’ strides out with a tribal bassy thump, igniting a high-pitched singalong. This is probably the most free and loose the pair of them have been throughout the entire set, it works. They’re the loud cartoon heroes in the playground of the future…

…meanwhile, Iggy Azalea is one of the cool girls at school who would never speak to you and only hangs out with older guys. She comes with bags of attitude, plus she’s wearing a pair of golden tits. They’re a must-have for any discerning rapper these days, Fiddy is begging for a pair. A merry-go-round set-up and DJ are just about squeezed onto the front of the stage, somehow leaving room for four booty-droppin’ backing dancers right at the front. On record she sounds exceptionally bratty, like Ke$ha with better hygiene, but her vocal delivery is far less annoying in the live arena. Set-closer ‘Work’ was probably the most unique thing on show, an honest track with a thoroughly catchy chorus and memorable lines. More of that please.

A big white sheet is hung up to cover a big black curtain being lowered. Thank goodness the freeloading plebs are restricted from seeing a black curtain being taken down. As Ellie Goulding watches from the balcony, huge screams erupt when the 60 second countdown begins.

The white sheet drops, and bits of it are wrapped around Katy as a wind machine makes everything look dramatic. She opens with ‘Walking on Air’, from her upcoming album, Prism. It has a strong House beat to it and the Dance vibe continues into a seamless uptempo mash-up of ‘California Girls’ and ‘Teenage Dream’. Just as you think this symbolises how predictable and inter-changeable Pop has become, she rips into the undoubted highlight of the set. An 80s synth intro disguises what would grow into a fierce guitar-heavy version of ‘I Kissed a Girl’. Perry controls the room with mic-stand in hand like Rock Gods of old, belting out her controversial hit in dominating fashion.

What’s pleasing is that she has a group of backing dancers who are pulling out some innovative routines, but she only becomes involved in a minor way. This is because she’s actually singing, unlike some of her contemporaries and forefathers (or should that be foremothers… is that a word?) It’s a key understanding that many in the Pop industry don’t get, if people buy your records they want to hear you sing them. A crowd doesn’t pay top dollar (although this show was free) to see a multi-million selling artist miming so they can do a few pirouettes, when they are surrounded by ten people already doing them.

Another highlight is the worldwide debut of her new album’s closing track, ‘By The Grace of God.’ Co-writer Greg Wells comes on stage to play in a piano that’s mostly hidden behind a large prism. It’s an honest ballad, possibly about her break-up with Russel Brand although the lyrics flirt with ambiguity enough to be applicable to a number of situations. It sits snugly between ‘Wide Awake’ and ‘Part of Me’, in a portion of the set that should be referred to as “Break-Up Corner.” While it’s not certain that all three of these songs are about her divorce, they are sung with the intense passion of a woman who has been burned. This segment finishes with Perry standing in the centre of the venue shooting confetti up from her hands.

Moving on from this, Katy tells the crowd that ‘Firework’ was for “anyone who has ever felt less”. At the overwhelmingly positive climax all of the dancers are stood with their hands raised to the sky; it feels less like a gig and more like one of those PRAISE THE LAWD religious sermons. Any minute now we’ll get a dude talking in tongues before old Grandmama Brown miraculously leaps up from her wheelchair and dances the Hoochie Coochie. Is this therapy to some people? I guess it can’t hurt if there’s someone out there constantly telling people that they’re special and can overcome any situation.

Half of a boxing ring is set up for ‘Roar’, and Katy dons a cheerleader skirt. There’s no encore, and for the grand finale we have… skipping. In terms of gimmicks it’s not quite Mötley Crüe’s drum kitor Society 1’s meat-hooks (seriously NSFL). It feels like a slightly underwhelming finish, treading water rather than emitting the titular tiger-like noises. Obviously she has to push the latest single, but there were numerous other songs performed (and some not performed) tonight that would’ve made better closing tracks. It’s a cheeky ten-song set that clocks in around at 40 minutes. A sickeningly uplifting, but ultimately fun experience.

For those unable to attend in person, all iTunes Festival performances will be streamed live to millions of fans in over 100countries via the iTunes Festival app, on the iTunes Store and with Apple TV so music fans can watch live on their iPhone, iPad, iPodtouch, Mac or PC and HD TV. The shows are also available to stream on repeat for a limited time. Check out iTunes for more details.