It is only a few months ago that a perfect storm of commercial pressures and internal conflict was poised to wipe out the 20-year-old festival for good. "But I don't believe in death by accountancy," West says. "As a creator of the event, I need to be the person who calls it, who determines that the event is over."

Music fans have big expectations of the Big Day Out, which for two decades has retained its tent-pole status as Australasia's top musical event amid successive waves of musical change. Unlike more specialised events, it was seen to champion any genre as long as it was cool; like Lollapalooza in the US, it wasn't just a concert, but a travelling show with multiple stages, an atmosphere of its own and wacky theatrical extras.

West and his partner, Vivian Lees, weren't the usual kind of entertainment moguls either; fans and followers of the music they were presenting knew them as fans themselves. West was the Sydney extrovert who talked a mile a minute, jumping between subjects unpredictably; Lees was quieter, identifiably from the arty end of Melbourne.

The hail of online criticism of this year's line-up, in which grunge rockers Soundgarden were a late inclusion as headliners and Kanye West will be a closing act only in the eastern states, thus constituted an event in itself. The problem was in the top line. West says Prince had approached the festival but never confirmed; Eminem was on the cards, but Big Day Out's offer of $6 million wasn't enough to close the deal. Scant early ticket sales confirmed the audience's sense of let-down.

And then came the crunch: after 30 years collaborating with West, Lees was leaving the festival he had shared in founding. In an official announcement, he said he was at a stage of life - aged 58 - in which he wanted to spend more time with his family. Behind the scenes, his relationship with West had finally reached snapping point.

Lees has kept silent - until now - about the split, but tells The Sun-Herald he remains unhappy about it. "I loved being in the Big Day Out and it was a very poor outcome for me," he says. "But I don't want to be negative about it because it's my legacy and I put a lot into it." He left, he says, at the point where they faced insolvency and urgently needed to recapitalise. "Ken wouldn't hear it. His response was not to look at it as a business proposition but to barge ahead and try to overwhelm me with his arguments."

It was the culmination of 10 years of tension involving a lot of telephone screaming between Sydney and Melbourne, he says. "It was appalling. I feel like I've been in an abusive relationship."

He was surprised when West offered to buy out his half. "I've no reservations about my decision. I feel strange being out of it when I've been part of it for 20 years but, at the same time, I couldn't work with him."

West found new partners in the US promoters C3 Presents, who back Lollapalooza in the US, and now owns 51 per cent of Big Day Out. This week he announced that the festival would no longer play in Auckland. "Every year we've agonised over whether to take it to New Zealand and it had to come to an end because it can't be subsidised from Australia any more, which it was," he says. At the same time, he and his new partners are considering branching out to Asia. "We're sitting down next week to go through all these things, to work out what the importance and essence of these things are. We want to be needed - not in a desperate and dateless kind of way, but you're only as relevant, especially with modern technology, as people feel you are. There's no standing on history."

Big Day Out had its beginnings in a Violent Femmes tour when the promoters West and Lees were looking for a middle-level support for their star act. They scored spectacularly by inviting Nirvana to join them at Sydney's Hordern Pavilion just before Nevermind was released, an event that turned into the first Big Day Out. "They got them for a good price and it took off from there.

They always had great taste," says Neil Wedd, a music industry veteran who worked as Big Day Out's promoter in Perth. "They've done it their way the whole time - not things that appealed to everybody, but mostly things they liked. They'd go overseas and say 'what's great?'"

But the turf has shifted under Big Day Out's Doc Martens. Specialist festivals have mushroomed and compete with Big Day Out for both bands and paying punters. The alternative scene that used to support the event no longer exists, having dissolved into the mainstream. Meanwhile, the event's original audience has aged to the point where most are not prepared to take a chance on anything new. West and Lees find that dispiriting.

"It's become Groundhog Day for me," says Lees. "We get criticised for putting on an up-and-coming band who'll be big in five years, which is what we're good at and what we need to sustain ourselves."

Tribalism rules, too: there was fury online at the news that Kanye West was playing, because he was seen as too soft. "They weren't looking from the positive point of view that he is one of the great creative musicians in the world at the moment," Lees says. "A big festival in the UK or the US can put people like that on but we have an audience that's closed to that. So it is disappointing."

He clearly wants to be optimistic about the event to which he devoted so much of his life. "I think that just as styles of music go through stages, so do festivals," he says. "It's lost market domination; it's just another entertainment option now.

''But I think there's nothing that can't be turned around with a line-up that crosses over different groups in the audience. Ken is trying very hard to keep the spark of life in it and he's brave for doing that."

Ticket sales have picked up now, according to West, as audiences register the depth of the line-up behind the headliners. In the years when tickets sold out within minutes of the announcements, he says, there was no opportunity to learn anything or to explain what they were doing. This year's crisis represents a "learning curve", he says, that was "very, very necessary".

Does it feel strange working on the festival without Lees? "Not at all! Not at all!" he says emphatically. "I gotta say no. It's still the same team, a few new faces but the same problems and same ambitions. It's just that we're working totally as one unit. I hate to say it, but it actually feels great. It feels like I've got a chance to start again."