You need the musical flexibility of an Olympic gymnast to be an Elvis Costello fan. It's not good enough just liking and understanding punk rock — the genre in which the young, angry, bitter Costello found his moment in the late 1970s. If you really want to keep up with him, you also need to like and understand country, jazz, soul and classical. An appreciation of easy listening wouldn't go amiss either.
In a career stretching over more than quarter of a century, Costello has dabbled in all these genres. He has worked with everyone from Paul McCartney to the Charles Mingus Orchestra, from Swedish mezzo-soprano Anne Sofie von Otter to German cabaret star Ute Lemper, from the Brodsky Quartet to, most productively, Burt Bacharach. He has sung with Bob Dylan. He has composed an orchestral score for a dance company. He has written an opera with Geri Halliwell.
Well, the last one isn't quite true, but you get the idea. And now, after last year's rock album, the man once dubbed a "genre tourist" has knocked out North, a rather fabulous album of ballads.
The question is, does Costello make a conscious effort to test his fans?
"No I don't," he insists, speaking in the sumptuous interior of the trendy London members' club Home House, sipping tea and sinking into a large leather sofa. "However, to make a record that is a repetition of something I have done before, simply because I believe it is commercially viable, would be a betrayal of myself and an insult to the audience. When people get impatient for me to make another rock 'n' roll record — which is a critical chorus I hear in England — I always say, 'you don't understand, it would be patronising to do something I didn't believe in'. But I don't deliberately try to be different with every record. I don't make plans in that way. I don't have ambitions. Things just happen to me. Opportunities come my way and I have curiosities which I follow."
He adds that he can tell from his live performances that his audience has changed as his music has changed — he no longer performs to rooms consisting mainly of "men in their 20s and 30s who live alone and don't know any women", and who dress like he did in the 1970s. "A lot of people have discovered me through the more recent stuff. There were people who had a passion for those early records and just wanted that repeated over and over — they went to find other newer bands that served them in that way. You can't worry about people who don't follow you — there's a lot of people in the world."
Costello's looks are as you would expect: half-shaven, with his trademark thick-rimmed tinted specs dominating his face, making it impossible to tell whether he is bored or engaged. And he is as demanding in conversation as he is in his music: his ferocious intelligence means it is impossible to get a simple answer to a seemingly simple question. Before you have even finished asking him something, he is picking apart the query and running away with some aspect of it. Take, for example, the rather straightforward question: would you say you were happy now? "It's always a dangerous thing to say, 'Yes, I'm happy', isn't it?" he begins. "I feel great reasons for joy at the moment, but it's a selfish thing to say, 'I'm happy'. It implies I don't care about anybody else's misery. Happy about what? Happy about my own circumstances? Yes. Happy about everything in the world? Obviously not. That's always a loaded question..."
His tendency to do this, combined with his well-known antipathy towards journalists and unwillingness to discuss personal matters, means that I am dreading asking the next question: does he mind that people are interpreting his new album as a commentary on the break-up of his 16-year marriage to songwriter and former Pogues member Cait O'Riordan, his subsequent desolation and his new relationship with jazz sophisticate Diana Krall?
"I think it's inevitable really," he says, shrugging and sighing, but proving remarkably relaxed about the subject. "But it won't make the songs one note better to know what relationship they have to my life — if you heard them in total isolation from knowledge of my life, they might still affect you. But I have no problem with people who think about that... Obviously I have entered a huge transition, and I don't want to deny the personal or intense nature of the songs because that would be doing the songs a different kind of disservice. But morbid fascination is just bad taste, apart from anything else..."
North is a fine record. Reflecting the changes in his life, the early songs are melancholic, the later ones buoyant. And from the opener, "You Left Me In the Dark", to the closer, "I'm In the Mood Again", all are very beautiful. The production is delicate: soft piano, gentle strings and tender trumpets accompany Costello's vocals. He says he is a little anxious about how such an album will be received.
"It's difficult to get a sense of emotion across in a record in a world that is shouting so loudly. The media, and music in particular, is so demanding of people's attention that it's very difficult if you make something that doesn't obey any of the rules currently thought to be essential. People can confuse gentleness of expression for a lack of feeling, simply because they have no reference points. There are no fashionable devices in this record either in terms of musical language or lyrical language — there's no irony or anything to create distance. It's straight on."
But, while he has produced a seriously mellow record, and despite (sort of) admitting that he is now actually quite happy, Costello has not laid to rest all aspects of the snarling young man he was 20-odd years ago, when he was reported to have kept a little black book listing the names of everyone who crossed him. He still has a capacity for annoyance and ire. Today, the man who left Britain for Ireland (although commitments means he spends very little time at his home in Dublin) reserves most of his wrath for English journalists. "I think there's a style of writing in England, when even when they're paying you a compliment, they have to couch it in slightly disrespectful terms because they don't want to be caught caring too much."
English critics who keep on comparing his new work unfavourably with his earlier work also get short shrift. "It's a peculiarly English (complaint), it's to do with the size of the country... in this country it has been harder to move on..."
Costello also — unsurprisingly considering the tense relationship he has had with record labels during his career — has little time for the way the pop-music industry now works. "I'm always longing to hear a new group that surprises me for more than the first eight bars," he says, qualifying the remark by saying that he does like the White Stripes and Radiohead.
"I think the machine of popular music and culture is so greedy now for new sensations that sometimes a group that sounds good is written off before it is given a chance to breathe and develop its first idea. I was lucky enough to at least get a couple of years to set a case for what I was doing. People are very impatient now."
However, the political anger that informed some of his earlier work seems to have gone — it's been a long time since he wrote something like "Tramp the Dirt Down", which begins with the image of Margaret Thatcher kissing a crying child in an NHS hospital, and in which he pleads that he outlive the former premier so he can jump on her grave.
Is he less political than before?
"It's a complicated question that we don't really have time for," he says, doing his pulling-apart-the-question trick again. "I've written a number of songs that people have called 'political', but I would say they were emotional responses to events and I don't know if that makes them political. Political to me implies they espouse some ideology or have some solution to propose, some sort of moral perspective, but they are often written to just make people feel less lonely.
"Nevertheless, I don't think you should keep writing things just because people might think less of you for not doing it. So, as yet, I haven't written my Gulf War song, or the 9/11 song that so many people feel moved to write. The complexity of the world we live in now makes it tougher to respond in musical terms. Songs of resistance are easier to write when there are obviously demonic forces like Adolf Hitler."
And Thatcher? "Yes. But when you have a government run by advertising men, you run into shades of grey. It's something to ponder — I don't want to shut the world out and just make escapist music. And I wouldn't say North is an escapist album because it's a series of love songs — I would say that in a world the way it is now, writing and singing about love is a pretty good thing to do."