Emma LeeIt's one of the most eagerly-anticipated shows of the Norfolk and Norwich Festival. Cult sister duo CocoRosie will be performing their beguiling 'freak folk' songs in the Spiegeltent. EMMA LEE reports.Emma Lee

It's one of the most eagerly-anticipated shows of the Norfolk and Norwich Festival. Cult sister duo CocoRosie will be performing their beguiling 'freak folk' songs in the Spiegeltent. EMMA LEE takes a glimpse into their world.

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At last year's Norfolk and Norwich Festival, audiences at shows in the Spiegeltent in Chapelfield Gardens quickly learned to expect the unexpected. So CocoRosie will fit in perfectly.

American sisters Sierra and Bianca Casady - the name CocoRosie comes from their childhood nicknames - started making music together in 2003, and their twisted fairytales soon had a cult following.

The sisters had an unconventional upbringing. Their mother was a Steiner schoolteacher, but they would spend their summers living on the road with their Shaman father.

The pair became estranged as teenagers when Sierra went to boarding school. She then moved to Paris to study opera, while Bianca lived in New York as a creative writing teacher, designer and model.

Then one day Bianca arrived at Sierra's flat out of the blue and discovered lots of common ground, including art, storytelling and music. And they've never looked back.

Their debut album, 2004's La Maison de Mon Reve, was by turns, romantic, satirical, disturbing, oddly sexy, impossibly gorgeous and, to some, irksomely pretentious. It was compared to everything from Billie Holiday to Puccini to 1980s rapper Roxanne Shante to Joni Mitchell.

So striking was the sound that it led to wild conjecture about just where this strange sound had emerged from. In fact, it was the bathtub of Sierra's tiny flat in Paris. The Casadys claim they improvised the songs while dressing in various costumes and drinking champagne. They both sang while Sierra picked out folkish patterns on an acoustic guitar and Bianca accompanied her by shaking costume jewellery, popping corks, rattling a coffee-grinder and manipulating one of those old-fashioned toys that moos like a cow when you turn it over.

That was followed a year later by Noah's Ark, which featured a collaboration with Antony Hegarty of Antony and the Johnsons, and then The Adventures Of Ghosthorse And Stillborn in 2007, which added heftier doses of old-school rapping to the lo-fi mix and featured a cover by renowned French artists Pierre et Gilles.

Their Norwich visit coincides with the release of their eagerly-anticipated latest album, Grey Oceans, which is the best yet at truly synthesising the weird world of CocoRosie.

It's just as weird but slightly less indulgent. Strange industrial hissing sounds accompany soft piano and a lightly plucked harps, with snatches of 80s G-funk breaking through. The sisters themselves float about in the mix with an almost ghostly presence, never quite pushing themselves to the forefront.

Vocally, they've been constantly compared to the likes of Bj�rk and Joanna Newsom over the years, but Grey Oceans establishes them as important voices in their own right. The sheer dexterity and variety of the performances across the album is astonishing.

The record was made all over the world - Sierra describes the pair as 'complete vagabonds. We are based nowhere' - beginning in Paris with the recruitment of new band member, jazz pianist Gael Rakotondrabe. Blending opera, electronica and folk using instruments ranging from harps to children's toys, they're certainly prolific songwriters.

'We wrote about 40 songs over the last couple of years and we selected a set of songs that would most represent our interest in spiritual taboo and in the future. Gael is a really strong influence,' Sierra says. 'It was recorded in several different studios, none of which had windows. They were all late-night sessions and had no relationship to the exterior,' she adds.

Lyrically, the new album is a bit of a departure. 'There's a lot of material that's influenced by the changing earth and the future of humankind, which is really new for us,' Sierra says.

'It's more serious. I think we've approached it in our own way. Our version is more hopeful, that all these changes the earth is going through is possibly a really positive thing, even positive for the human race, and imagining our future and what we are going to act like, what kind of music we are going to be listening to.'

Highly in demand on the live circuit, CocoRosie's live shows have included everything from a trapeze artist to special costumes and a one-off collaboration with the Royal Dutch Orchestra at Amsterdam's Concertegebouw. And Sierra promises that their show in Norwich is going to be 'energetic and rambunctious'.

'There will be five of us on stage. We have a beat-boxer with us, we've been travelling with him for a few years. We'll also have our percussionist play some really home-made equipment, drums made of car parts and pans,' she says.

Outside of the band, Bianca is an accomplished artist and costume designer, with recent shows in New York, Groningen, Milan and Brussels. In Brussels, she exhibited in 2008's It's Not Only Rock'n'Roll, Baby alongside work by Brian Eno, Patti Smith, Yoko Ono and David Byrne, a noted fan who invited the sisters to perform at New York's Carnegie Hall.

The sister greatest work of art though is themselves.

t CocoRosie play the Spiegeltent in Chapelfield Gardens on May 13, 10pm, �17.50 (under 25s �5), 01603 766400, www.nnf10.org.uk

t Grey Oceans is released on May 11.

t Further listening: www.myspace.com/cocorosie