Split open the head of Jamie xx and you might expect to find an image of post-industrial sadness – an empty ferris wheel turning in the rain, perhaps, in the shadow of a smoke-belching chimney. This is what greets you on the approach to the abandoned GDR theme park the xx have chosen for their second Night + Day, a series of atmospheric one-day festivals in "locations of great beauty" featuring music, and food, chosen by the band.
The first show took place earlier this month at Lisbon's 16th-century defence tower Torre de Belém, and the next is at Hatfield House, Hertfordshire on 22 June. Spreepark in East Berlin, which fell to ruin in 2002, is a symbol of the city's "ostalgia", the lingering affection for the paraphernalia of Soviet grimness. Berliners do urban decay so well, and the xx make music for graffiti-covered subways and deserted car parks. This is a flawless match of sound and physical space, and here the overused word "curation" feels appropriate for a music event.
The wet trees shudder with sub-bass from German DJ Marcus Worgull and transgender Californian rapper Mykki Blanco warms up the main stage. Apart from illegal raves, it's the first concert in Spreepark and, passing a couple of concrete elephants with "achtung!" signs round their necks, I'm starting to think health and safety have fenced most of it off when I notice the ground under my feet has turned into faded blue plastic and I'm tracing the dried-up bed of an ancient log flume.
The structure feels perilously thin, suspended over an artificial pond choked with two decades of duckweed. In the distance, four adventurers in different coloured macs climb into the black mouth of an old rollercoaster. There's a fallen T. rex, its belly smashed open, which has clearly been slept in. At many points today, largely due to the sheer physical hazard, I feel sick with excitement, and that's one emotion I don't usually associate with the xx.
With their shady remix of You've Got the Love, the band showed their interest in casting 80s soul in a sober new light. Womack & Womack's Teardrops and Anita Baker's Sweet Love pop up in a set by the London-Kreuzberg funk guru Kindness; Tic & Tasker's DJ hour is full of mirrorball disco, sax solos and tiny musical in-jokes – handclaps sampled from Another One Bites the Dust, "urghs" from James Brown. When these songs were first on the airwaves, these fairground rides were shiny and new.
A producer's mindset permeates Night + Day, but in the past few years someone has realised that if this kind of breathing, digital electro-soul really is the music of the future, you have to present it properly. Like Jamie xx, London's Mount Kimbie are fun to watch: when they're not bobbing over knobs, they're plugging away at synths like Keith Emerson. One of their best electronic effects is a gurgling reverb that sounds like a sinkhole at the centre of the earth. And here's the strange thing: all this music, half of which emerges from computers, makes so much more sense live.
There won't be many gigs at Spreepark before someone accidentally chops their head off on one of the abandoned rides but the atmosphere tonight is calm, echoed in the sweet posters the band have left everywhere "thanking everyone for this sell-out show". Oliver Sim keeps saying, in his shipping forecast/sex-line voice, that the event is "like a wedding" because there are so many people to thank. It's a good analogy given the stylised, imaginary love affair between him and Romy Madley Croft which Jamie, like the awkward third wheel, does so much to dramatise. Sim lollops around in the searchlights like Peter Hook.
They feel more present than in their early gigs, theatrical performers unembarrassed to break the fourth wall and enjoy themselves. They do their own version of that awful song from 2000, Modjo's Lady (Hear Me Tonight) – which clearly sounds like a classic to them – and Stardust's Music Sounds Better With You, which sounds like a classic to everyone else. It's weird and heartening hearing 10,000 people screaming over steel pans, while Madley Croft's Tracey Thorn-style jazz voice keeps them grounded in the analogue world.
Over the past three years, the xx have created a delicate, meditative space in which you can watch the components of music being carefully put together. Tonight, even those who never made it to the main stage and remain somewhere out there in the darkness, tracing the toy railway round the edge of the woods, are having an interactive experience.
