"I had all the pop success I could take. I was sick of it," says Elvis Costello, pondering that brief period when he was the hottest songwriter in the music business, the new wave's answer to Bob Dylan.
"I was ready to quit in '79 because it's an empty thing to just have a bunch of uncomprehending teenagers waiting for you to sing 'Oliver's Army' because that's what they've seen on Top of the Pops.
"Every time I have a hit it becomes a burden, a thing that you've got to drag around to the next bit of your career. There's got to be more to life than having been famous for half a dozen songs. I didn't want to make it bigger and bigger, so I took a different route."
Actually, Costello took several different routes, often at the same time, weaving a highly erratic path through pop culture. Certainly one of the most brilliant and arguably the most eclectic musical talent of our times, on Monday Costello releases two albums simultaneously. "Just the mere two," as he puts it himself. "I haven't gone completely mad!"
The Delivery Man (released by Lost Highway) is Costello's most fully realised collection of songs since his '80s heyday, a raw and slightly ragged album tinged by country darkness, full of barbed emotion, rich melodies and sharp, lyrical twists.
In contrast, Il Sogno (Deutsche Grammophon) is Costello's first full-length orchestral work, an adventurous and almost skittish blend of jazz, swing and classical performed by the London Symphony Orchestra. It was commissioned by Italy's Aterballeto dance company for their adaptation of A Midsummer Night's Dream.
Such diverse releases would be extraordinary by any musical standards, but they represent only a fraction of Costello's output. When I caught up with him recently in New York, he was celebrating his 50th birthday by performing three entirely different concerts at the prestigious Lincoln Centre, covering 70 different songs, from punk rock to bebop, backed variously by a Dutch jazz orchestra, the Brooklyn Philharmonic and his own rock band, the Imposters.
"All the music comes out of the same head," says Costello. "It's just using different methods to get at the solution to whatever motivated you to write in the first place."
Costello is a musical polymath, with enormous artistic curiosity, a wide-ranging intelligence and a very quick mind. Sometimes too quick.
He is not always an easy man to interview. I have met him several times before and, despite being a fan, found him a rather spiky, combative and vaguely paranoid individual, prone to finishing your sentences for you (not always as you had intended) and with a tendency to take things the wrong way.
Yet, in the middle of an absurdly hectic schedule, when his frantic activity might have been a legitimate excuse for brusqueness, Costello proves unusually relaxed and good humoured.
Married (for the third time) to acclaimed jazz chanteuse Diana Krall, the tenderness with which he addresses his wife when her phone call interrupts our interview suggests personal happiness may be at the root of his altered mood.
A close mutual friend remarked that Costello is "a testament to the power of love." Costello smiles at this notion, but does not (for once) immediately embark on the case against.
Born Declan McManus, Costello's father, Ross, was a big-band leader and Costello's early albums display a musicality more advanced than was generally heard in the punk movement.
When I asked what drew him to identify with punk he smiled. "It was just direct and argumentative, and, as you know, I'm a bit like that myself. But I never bought the year-zero idea of punk. Punks just had a shorter catalogue of musical reference points than I did."
Costello then launches into a dizzying monologue about the historical development of Western music, encompassing the harmonic innovations of Bach, Debussy's appropriation of Balinese gamelan music, the reinterpretation of classical concepts in film music, and the ambient theories of Brian Eno.
"There are a lot of uses of different ideas in music that keep coming round. You get these emotional explosive things like punk rock: dismissal of the status quo is as important as innovation, isn't it?
"So you get people challenging the previously held view of harmony and you get surrealism and atonalism. Well, that's one way to go. Some of them can be cultural movements and some of them are actually technical and aesthetic changes."
Oddly for such an avowed music lover, Costello considers himself a limited player.
"I don't think in schooled terms. I play the guitar and piano in pretty rudimentary fashion. I can hear relatively complex things and imagine them, but, no matter how much you learn, it's good to keep a bit that's really primitive."
He learned to read music only 10 years ago after becoming "frustrated and embarrassed" that he couldn't make himself more clearly understood when working with classically trained musicians, as he has done on TV soundtracks for Alan Bleasdale, and with his compositions for the Brodsky Quartet and Anne Sofie von Otter.
"Once I learnt how to write music down I could determine musical values more precisely while keeping this idiot version of myself somewhere in there, in the compositional side, which is the same guy who picks up the guitar and thrashes out a song."
The strength of his musical imagination is reflected in the direct process by which he composed the 200-page score of Il Sogno without actually picking up an instrument.
"I was imagining the entire orchestra in my head and writing it straight down, chord by chord, line by line. I didn't know it was such a big deal until I told some more experienced colleagues.
"I think when you hear orchestral music written on the piano, it sounds to me like an expanded piano. I'm doing a lot of things that aren't natural to any instrument, really. I've kept the primitive thing at the heart of it."
For a while he thought he might never write lyrics again. "You start out having the music just serve the words, and then you start writing music that can carry some meaning and some weight of feeling on its own. It gives you a lot of freedom."
But it is hard to imagine such a verbose individual giving up on words altogether, and it was not long before the songs started coming.
The Delivery Man has the energy and concision of Costello's classic early work, with the added weight of emotional maturity in songs that deal with the disappointments of ordinary life and the dark allure of sexual temptation, all set against a political landscape of fear and confusion.
In keeping with Costello's restlessly creative ambitions, there is a narrative concept lurking in these songs, although it will only reveal itself in full over the next three albums.
"I don't want to tell it all at once. I want to let people engage with it, make their own version, because everything I do is about imagination. That's the job. I'm not making records to make people dance. I'm making records to provoke certain responses, to try to stimulate people's feelings."
After a discussion of the narrative form in pop (with reference to rock operas and the work of Bruce Springsteen), I ask why Costello doesn't write a book. "That's next," he says, confidently. Why am I not surprised?
It will take its cues from certain songs and contain, he says, "all the things that would be of use in a biography but not told in strict biographical terms. In other words: point of view, disposition, passion, experience, but told in character form.
"I'm not interested in autobiography: I was born, then I had this tragedy, then I rose above adversity. There's a more interesting book to make out of life than that."
He confesses that he is not sure if he can pull it off but then adds that is how he feels about most things he tries.
"I don't want to do stuff that's retailing a formula. I could write 'Oliver's Army 2004' and it might be a hit, but what would be the purpose of it? I know I'm different from lots of songwriters. I don't think I'm better than everybody else but I'm the best version of me."