Sins and the saxman: Soweto Kinch

"In Dante's Inferno, or any of the writings of medieval demonology, sin is always quite fantastical," he says. "Even in modern discourse it can seem quite remote, whereas in our day-to-day existence sin is actually endorsed and encouraged." He looks round the empty Sadler's Wells café. "Greed, status envy, lust - they are so innocuous that you don't realise that you've been taken over. And it's society that encourages us."

Kinch's laid-back demeanour - his traveller's beard, steadily growing Afro and booming laugh - belie strong convictions. Now 34, he is a free agent (he left his label Dune in 2007) and it clearly suits him. He has never quite conformed to anyone else's expectations.

Kinch first appeared in 2003 and soon found his voice by combining improvisational jazz with his first love, hip hop (in addition to being a mellifluous, fiery altoist, he is a fierce and witty MC). He often works in a narrative setting.

His 2006 concept album, A Life in the Day of B19: Tales From the Tower Block, dissected the Birmingham high-rise where he still lives, and featured a narration from Moira Stuart ("Let me give you a tip Mr Intelligent Black Man/Put down the microphone and stick to the sax, man," runs one lyric, pre-empting the backlash from his jazz peers).

His most recent album, The New Emancipation (2007), was inspired by the 200th anniversary of the abolition of slavery and informed by Kinch's own emancipation from Dune. "Perhaps the most pernicious and resilient aspect of slavery was to persuade Africans to accept and even perpetuate the terms of their own enslavement," he wrote in the album's liner notes -though that might give you a false impression of the lyrics, which are closer to the urban comedy of The Streets or Smiley Culture and are frequently hilarious.

The Legend of Mike Smith will hopefully be ready in time for the London Jazz Festival in the autumn. Meanwhile, audiences can see the work taking shape at the eXplorations festival at King's Place next week.

When I first encounter Kinch, he is programming beats on his laptop, immersed in creation. He is due to have his first rehearsal with his collaborators, choreographer Jonzi D and dancer Tyrone Isaac Stuart, at Sadler's Wells later today. The concept has been informing his composition in fascinating ways, he tells me, allowing him to adopt a slovenly approach to rhyming for "sloth", say, or getting the music to sound as fat as possible for "gluttony".

He has also been drawing on his Oxford history degree to develop the theme. "There is always a complex hierarchy of business interests, throughout different ages, to exploit our natural weaknesses," he says. He has been listening to a lot of baroque church music, particularly Bach, working out how to reframe harmonic counterpoint in a hip-hop vernacular.

At various points, Kinch has to bring me up to speed on Dante's Inferno, the spread of Catholicism in Europe and Evagrius Ponticus, the Egyptian monk who first conceived the idea of the seven sins (did you know there were originally eight, but dejection and apathy merged to form sloth?)

What really animates him, however, is an acute moral consciousness. He has toured extensively in the past year, performing with musicians in Africa, Europe, the Middle East and America, and he has not been travelling with his eyes closed.

"I've had similar conversations with people from all different classes and strata of society - and they're chiming. People feel the oppression of big business, they feel the corporations bearing down on us," he says. Indeed, a conversation with Palestinian MCs about their fear of UN recognition leading to exploitation by Western companies helped shape his thoughts about corporate greed.

"What are the grievances, funda-mentally?" he asks, drawing parallels between the uprisings across the world. "A sclerotic and insensitive political elite who continue to bail out the same corporate interests; youth unemployment and lack of opportunity for a whole generation of people; slavery-like conditions when it comes to financing property ..."

He was most affected by his visit to the Holy Land, where his keen sense of irony kicked in. The Christian pilgrims he met were more interested in kissing sacred stones than engaging in the political injustice around them. "Surely Jesus would have been more incensed about these real inequalities, militarisation, removing people from their own lands?"

The fire and brimstone is in his blood. Kinch's father was a Rastafarian playwright and community activist. Soweto, who was born in London, grew up in Handsworth (the Brixton of Birmingham, roughly speaking) and was sent to private school. His upbringing had a strong religious flavour, and it continues to drive him. "The process that I'm exploring with this work is partly about getting truly free of those sins that distance you from yourself and from God," he tells me.

I tell Kinch he seems comfortable on territory that most musicians would run a mile from. He shrugs. "If you are a feeling musician and someone who wants to make work that speaks to people, you can't help but be affected by this stuff."

In any case, the "stuff" arrived on his own doorstep, in fact. Kinch's own tower block was at the centre of the summer riot in Birmingham. He was in Hackney at the time but returned to find the community he had portrayed in his music riven with discord (21-year-old Haroon Jahan was killed a five-minute walk away from his estate). Since then, he has watched the fallout with growing frustration.

"It felt like I was back in the Eighties again. There was this 'cross over the road clutching my handbag' vibe again. It's always there but the minute there's an economic downturn and some reason to associate black people with criminality, it comes out again."

He believes we have regressed in our treatment of race. He is furious that Newsnight saw fit to welcome on a black former gang member to discuss the Stephen Lawrence verdict. "What's the connection between a gangster and somebody who wanted to be an architect? It's almost as if there's a subtle thing within the media to make 'black' conterminous with 'crime'."

He cites the recent controversy over the Liverpool footballer Luis Suárez, who racially abused Manchester United's Patrice Evra. "I think our eyes are always off the prize with that. I mean really, do I care if someone calls me a coon on a football pitch as much as I care about being given a fair shot at managing a Premiership team?

Representation, opportunity, a fair slice of the pie - these are profound issues and they are more to do with class and opportunity than someone calling someone a nigger on the football pitch."

Does he think music has lost that ability to provide moral leadership? "Music will never lose that power. But the music industry has definitely surrendered that because everything is so intensely focus-grouped."

He says he can't see why more artists don't do as he has done and say goodbye to their labels. "It's a liberating time for the artists again, to take over their own means of production, to find their own audience."

He did that himself when he took his sax down to the Occupy London protest at St Paul's Cathedral and videoed his performance for YouTube, and cites the musical response to the summer riots as proof that musicians are socially engaged.

Still, I'm a little surprised, when I ask which living musician he most admires, that he says Wynton Marsalis. The virtuosic American trumpeter is an avowed traditionalist and has been staunchly critical of hip hop in the past.

"He's not anti-hip hop - he's pro- jazz," corrects Kinch. "The last conversation I had with him, he said, 'You wanna do that, go ahead and do it. You believe in it, I endorse it'. That's what I admire most - his integrity."

And while Kinch's artistic vision does permit jokes, it has the same high seriousness. "My raison d'être is to be as excellent as possible. Really, I want to be as virtuosic an MC as I possibly can be, to improve as a saxophonist and as a composer," he laughs. "I think that's the only responsibility a musician really has."

Soweto Kinch performs on Friday January 27 as part of the eXplorations festival at King's Place, N1 (020 7520 1490, kingsplace.co.uk).