The eighth album from musical innovator Nitin Sawhney, London Undersound, is a work of extraordinary variety and vitality. Featuring a cast of guest contributors that includes Natty, Reena Bhardwaj, Ojos de Brujo, Anoushka Shankar, Roxanne Tataei, Tina Grace, Aruba Red, Imogen Heap, Faheem Mazhar and Paul McCartney, the album embraces a far-flung range of musical and cultural influences, to put it mildly. And yet the collection is deftly bound together by Sawhney's masterful production, and a narrative subtext which runs through the diverse strands of music like a thread of steel.

''London Undersound is about how London's changed since 9/11 and how I and other people perceive that change,'' Sawhney explains. ''I don't recognize London as the same place it was ten years ago. The change has been quite subliminal and insidious. But it is massively different. London has become polarized in a way that I find uncomfortable and threatening, especially as an Asian person. I wanted to explore through my music the dynamic of a city which is going through a major transition.''

The album explores some difficult themes. But London Undersound is certainly not a negative polemic against London, the city which, after twenty years, Sawhney still calls home.''I don't want it to be all doom and gloom,'' Sawhney says, smiling. ''And I certainly don't think of London in that way. The piece was meant to be purifying as well. It's music that washes away all the impurities that can populate your mind.''