Folk, jazz, classical, electronica? The music of Spiro is difficult to classify. But with the likes of Peter Gabriel fans, they're garnering plenty of acclaim. SIMON PARKIN reports.

Though you'll probably find their albums in the folk section, Spiro are something of a slippery beast when it comes to being contained by musical description.

Despite the group's folk-friendly tools — violin, acoustic guitar, mandolin and accordion —they are not easily pigeonholed by mere musical genre.

'We?ve got as much to do with minimalist classical and dance music as we have with folk,' says guitarist Jon Hunt, when asked how he'd describe the four-piece who perform at Norwich Arts Centre next week. 'Even though we use folk tunes, they?re raw materials that the rest of the sound is built around.'

'We're like a string quartet, but the most driving and exciting string quartet that you could imagine,' adds violinist Jane Harbour.

One thing is certain — Spiro are their own people, operating in their own sphere and at their own pace. This contemporary acoustic ensemble first came together through Bristol?s folk sessions scene in 1993, trading under the name of The Famous Five.

Their individual backgrounds are wide-reaching. Harbour studied classical violin in Japan under the legendary Shinichi Suzuki. Accordionist Jason Sparkes began his own classical training during his pre-school years before taking up folk at the start of his teens.

Alex Vann was the drummer in a punk band before taking up the electric guitar and then graduating to his weapon of choice — the mandolin. Hunt has also done his time in punk bands, someone who took an unusual route from pop to folk to punk to post-punk/new wave but emerged with 'this preserved love and fascination for traditional English music'.

The musical heritage of Northern England is at the heart of the quartet's sound, but Spiro has grown in the near 20 years since they first came together. Folk structures have given way to minimalistic classical elements. The sound has absorbing contemporary electronica.

The outfit arrive in Norwich in support of Kaleidophonica their second album on Peter Gabriel's Real World Records, their fourth album in total.

Gabriel himself has long championed the band. 'The sounds that hit you first are sounds that you are familiar with; they sound folky, but once you start listening to the music and how it's composed you hear elements of systems music – people like Steve Reich, Philip Glass, dance music,' he has enthused.

Kaleidophonica took 18 months to write — in contrast to Spiro's much-praised previous Real World album, Lightbox, which evolved over 10 years.

The album title — meaning 'beautiful sound forms' — gives a clue to music. It's an album of extremes – where chilled tracks, sit alongside some more intense acoustic dance music.

It marks a progression from Lightbox. 'We've pushed the ideas and the systems music further,' says mandolin-player Alex.

'We've taken the most intricate bits of Lightbox and taken the whole mesh to a higher level,' adds Jane. 'And if it sounds as if there are more than four of us playing, it's because much of the time people are playing more than one part at the same time. We try to play two lines on one instrument quite a lot, so at some points there might be eight lines going on.'

Like Lightbox, the album was recorded live in the studio with no overdubs. Most of the tracks are completely original compositions, with a handful based on traditional folk tunes.

All four band members contribute to the song-writing process, suggesting either riffs or tunes.

Jane is crucial to the process of bringing the sounds together according to Jon. 'Her head is like a multi-track studio. She can hear complex arrangements, and manipulate them in her head.'

While Jane, Alex and Jason Sparkes mostly provide the riffs, it's Jon who adds the traditional melodies. 'I've always been Mr Tunes', he said. 'I love traditional tunes and particularly tunes from the North-East and North-West. They resonate with me, and I'm always pushing them into the pot.'

The five traditional tunes that remained in the Kaleidophonica pot include Saw Ye Never A Bonny Lass, transformed into the track The Gloaming, and Softly Robin, which was collected by John Offord, which has kept its original title.

Despite a slew of work for theatre, film and television, Spiro still remain something of an enigma. 'There was never a grand plan,' explains Jon. 'It's just evolved.'

And with such a diverse sound who can we expect to see in the audience when they arrive at Norwich Arts Centre, where they'll be supported by Cliff Stapleton, of Blowzabella and Coil?

'People from all genres — classical fans, dance music fans, folk and jazz fans,' said Alex. 'And there are teenagers and octogenarian fans. There doesn't seem to be a particular world that we belong to.'

? Spiro play Norwich Arts Centre on March 27.

? Kaleidophonica is out now.

? Further listening: www.spiromusic.com