Radiohead's Thom Yorke has said a track on his solo album about the suicide of scientist Dr David Kelly is "the most angry song I've ever written".
Yorke has said his solo album does not mean the end of Radiohead
He said he was uncomfortable discussing Harrowdown Hill out of respect for the "grieving" family of Dr Kelly, whose death led to a government inquiry.
He told the Observer Music Monthly he recorded solo material because being with his group was "getting boring".
Yorke said sleep deprivation on a world tour had left him feeling "messed up".
The song Harrowdown Hill was named after the location in Oxfordshire where Dr Kelly's body was found in 2003.
He had been identified as the source of a controversial BBC story about a British dossier on whether Iraq had weapons of mass destruction.
"I'm sure they're still grieving over his death," Yorke said, referring to the scientist's family.
"It's the most angry song I've ever written in my life. I'm not gonna get into the background to it, the way I see it.
"And it's not for me or for any of us to dig any of this up. So it's a bit of an uncomfortable thing."
Dr Kelly's death in 2003 sparked an extraordinary chain of events
The musician has previously insisted his solo album - entitled The Eraser - was recorded with his fellow bandmates' blessing and does not mean they are splitting up.
However, he admits that he was left exhausted by Radiohead's Hail to the Thief tour, which went around the world from east to west, meaning he was frequently jet-lagged.
"You're not built to do that. It just spun our heads out, man," he said.
"I don't think anybody really slept for, like, three, four weeks. So that level of sleep deprivation and doing these big shows under lot of pressure... It was just messed up."
Spending so much time with the group "was getting boring", he conceded.
"It felt like everyone was under obligation to do it rather than because we wanted to do it.
"And one of the things I had wanted to do for ages was get stuck into a bunch of things that I had been mucking around with that didn't fit into the Radiohead zone."
'A different context'
The Eraser - produced by Nigel Godrich, involved with Radiohead albums including The Bends and OK Computer - was "an accumulation of really sketchy ideas that were going around since I learnt how to use the laptop properly", he said.
"It didn't feel right" to release it on Radiohead's record label EMI, he told the magazine. The smaller record company XL will issue it instead, on 10 July.
"It was done with the doors shut... without anybody watching. And it was done in a different context so it felt like it should be put out in a different context.
"Which is not saying that we won't put things out through EMI or whatever. I just don't personally feel that we owe anybody anything."
Asked if Radiohead would re-sign to EMI, he replies: "I don't know. I don't think we'd sign to anybody. Give someone a record when it's done if we feel that they can do it justice. That's it."