Observations: Tribute to lost leader of EST

Few artists get to change the very definition of the form in which they work, but the Swedish trio EST's mix of lyricism and thunder, shaped by its leader Esbjorn Svensson's brilliantly melodic compositions and underpinned by the group's telepathic improvisations, permanently redefined the boundaries of jazz. Even fewer artists opt to step off the production line that is leading them to success. But Svensson was no ordinary artist. Siggi Loch, the head of his record label, ACT, remembers him getting "all these offers to play last winter, but he said, 'No, I'm taking three months off, I'm taking my kids out of school, and we're going on a world tour'."

And so they took off to Japan, the American West Coast and Australia, where Svensson discovered a new passion for diving. But in June, tragedy struck. Just after the band had signed off their latest album, Svensson was killed while diving with his children off the island of Vramdo, near Stockholm.

The band formed in 1993, when Svensson joined up with the hard rock-influenced bassist Dan Bergland and the drummer Magnus Ostrom, a childhood friend. On Sunday, the two musicians will take part in a special London Jazz Festival tribute event at the Queen Elizabeth Hall, in which they will remember their band mate and introduce previously unseen live footage.

It was in 1999 that EST signed to ACT with their breakthrough album From Gagarin's Point of View, and they soon became known for their rock-concert like gigs, complete with dramatically designed lighting. Theirs was a bottom line that ranged from Monk to Metallica, funk to electronica, thriving on chance operations as much as perfectly drilled compositions. Their last recordings were a radical departure even by their eccentric standards. With Leucocyte, they walked into Studio 301 in Sydney during a tour and, over just two intense sessions, recorded nine hours of completely improvised, unprepared music – cut down to around 70 minutes for the album.

Its stunning centrepieces, "Premonition" and "Leucocyte", trip through the bloodstream like a powerful drug, building on dubby electronic distortions and a spare drum and bass riff to rise up into monstrous, almost terrifying explosions of drum salvos, bass lines and piano chords, sent spinning through an array of microphones and effects boxes. This is music-making without a safety net.

"When I first heard it," says Loch, "I called him up and said, this reminds me of Pink Floyd's Dark Side of the Moon – it was such a departure, even though everything you know and love about EST is in there."

"We played from our hearts – it's music raised from very deep inside," explains Ostrom. "For me, it was very much about life. And it's a very absurd situation because of what has happened."

Esbjorn Svensson Celebration, Queen Elizabeth Hall, London SE1 (0871 663 2505; www.southbankcentre.co.uk), Sunday, 2pm; 'Leucocyte' is out now on ACT