 'If you're walking down the road and see a poster that said, 'Tonight, Bob Geldof', people wouldn't recoil from that," muses the man himself. "Then 10 yards up the road they'd go, 'Doing what?'" Geldof laughs. "They've forgotten that music is what I do. Everything else is peripheral. The spine of my life is entirely music. I think in terms of it, frame my references to the world through it, articulate myself through it."  Geldof recalls listening to Radio Luxembourg, late at night, during a very unhappy childhood in the Sixties. "age 11, I was struck with the absolute realisation that these boys and girls were articulating other possibilities, other universes, the necessity of change, the desirability of change, the inevitability of change. Here was the language for change, and here was the instrument to implement change. It was a musical eureka moment: the possibility of change."  Geldof became a musician but he also became an agent of real political and cultural change, through his instigation of Band aid, Live aid and relentless campaigning for Third World debt relief and other global poverty issues. With his new wave band, The Boomtown Rats, he briefly topped charts in Britain and Europe in the late Seventies, but he only really achieved worldwide fame as a belligerent, fearless and frequently foul-mouthed charitable activist.  "You know the John Lennon song, Julia: 'when I cannot sing my heart, I can only speak my mind'? Well, I have every opportunity to speak my mind," says Geldof. "If I want to write about economics, I can write for the FT or the Telegraph. I have done! If I want to make a speech about debt reduction, I can make a speech to world leaders. If I want to get on Newsnight and talk about global poverty, I'll be on. What I'm not allowed to do is sing my heart. and that's something everyone needs sometimes."  Geldof has just made an album, called, with self-mocking irony, How To Compose Popular Songs That Will Sell (released this week by Mercury). It is his first in nine years, and easily his best since the early albums of The Boomtown Rats. alternately intimate and pugnacious, reflective and uplifting, richly melodic, lyrically eloquent, hugely stylistically diverse and bristling with hooks, he seems to have rediscovered his pop nous, his musical mojo. Bob Harris, the veteran Radio 2 DJ, has already called it the "album of the year", and it has put Geldof at number two in the Irish charts, the dizziest heights he has occupied since his all-star, charity singalong Do They Know It's Christmas held the number one spot for five weeks in 1984. "My thing was get inside, have hits, talk about things that were important, change it. But what somehow got lost was the music. Playing live, without any question, is my greatest pleasure. I've got an amazing band that I can relax into, enough people come and see me, out of curiosity, probably, and it is entirely cathartic, I disappear into it."  I have encountered Geldof over the years, and he is almost visibly a happier person now, somehow lighter and less burdened, a state his songs appear to confirm. There are spikey, dark moments but it is a very uplifting album, full of celebrations of the redemptive power of love. "all things considered, my fifties were the best decade for me. You never expect that. I'm at the beginning of my old age, things get easier. The sexual , professional and economic imperatives are less. It's not less important, just less driven."  The last time Geldof released an album, Sex, age and Death, in 2002, it was a brittle, angry, depressed affair. Its chief inspiration seemed to be his "faithless wife" (as he calls her on Popular Songs). Paula Yates left Geldof in 1995 for rock star Michael Hutchence, instigating a tawdry, drug-fuelled drama that left both Yates and Hutchence dead, and Geldof assuming custody of their daughter, Tiger Lily, to raise alongside his own daughters, Fifi, Peaches and Trixi. Geldof 's own mother had died, suddenly, when he was just seven, and the Yates affair seemed to breach a dam of dark emotion. "I've been around a lot of death, in africa and personally, seen too much dying," he says. "all of that stuff, your mum, when you're a kid, it just happens, you get on with it. I don't remember grief for my mum, or bewilderment, so that surges out with all the Paula stuff. Bereavement, absolutely unbound. It was overwhelming, this amorphous mass of loss and pain." Songwriting, he believes, was crucial to his recovery. "The impulse to music is about framing your references to the world. You're trying to flesh out a sensation, find something that is essentially incoherent, certainly inchoate, and make it tangible. Until I'd done that, I couldn't understand what had happened to me."  The new album, then, could be said to celebrate the woman who saw him through tragedy, his long-term girlfriend, the French actress Jeanne Marine. "When you're at your most detestable, most ugly, not capable of responding to another person's emotions, that somebody would stay the course with you tells you there is still something in you that's loveable. and it turns out that all those crappy, corny songs are true. Love is all you need, love is the answer; it's hugely redemptive and powerful, as we all know, except it took me a long time to get there."  The album comes on the end of a period of some personal grief. Geldof's father, Robert, and his sister Chloe (who effectively had to mother him as a teenager), died within three weeks of each other in October.  Geldof speaks very movingly of both, although his acceptance of his father's death at 96, tired of the indignities of ageing, ("my sisters held his hand and kissed him, as I did, but I said 'nothing bad happened here, it's all good stuff'") is very different to his response to his sister's sudden and unexpected passing, aged 69. "That was the worst. Because your siblings are rivals, you support each other, they are the ones who tell you ruthlessly to your face who and what you are. Then that unit is no more, so your mo 