There are two Nigel Kennedys. The one who `likes to arse about' (his own words) and the daring virtuoso whose reading of the Elgar Violin Concerto leaves conductor Simon Rattle feeling that a journey has been made into territory never before explored. By Edward Seckerson
Inside Symphony Hall, Birmingham, they're making a record. But nothing stirs. It's as if they have finished early and gone home. Then you hear it: a mysterious thrumming in many strings. A strange, distracted sound like something in nature shifting. Or someone walking over Edward Elgar's grave. The final pages of his Violin Concerto - the longest and grandest in the entire repertoire - are among the most extraordinary ever penned. This is the hinterland of the concerto, a place where dreamers come to dream, where only the past makes any sense and even that is just so much ephemera. Elgar remembers, the solo violin remembers: what has been, what might have been. But there's no going back. This particular soloist knows the feeling well. He has passed this way before, he may do so again, but this moment, this here and now, is the only one that really counts. And it's full of wonder.

Moments later, that familiar figure is striding into the control room to check out the playback. The haircut still has attitude but the Doc Martens have been traded in for a pair of M&S slippers. More comfortable. And quieter, too. As ever, his own assessment of the situation is measured and concise: "Still fucking up the same bits I did last time, maestro..."

Nigel Kennedy is back. And try as we may, we still can't reconcile the player to the playing. Four years ago, the man whose record sales have long since topped 4 million, the man who took "Viv" (that's Vivaldi as in Four Seasons) into the pop charts, who was all over the classical music establishment like a rash, decided that he'd had enough. His record company, EMI, had gone out and done the business, but the business had done for him. His concertising was turning into one long promo tour. The music was getting left behind. He was losing control. As he said at the time, if Four Seasons II had been an option, EMI would have had it out in time for Christmas.

So Kennedy took to the Malvern hills with the proceeds of Four Seasons and the rest was silence. At least that's how the public will have perceived it. But behind locked doors, in camera, and sometimes not (there were impromptu concerts in local churches and the like), Kennedy was hard at work, "jamming" with friends - chamber music, jazz, or whatever, the principle of the shared experience was the same - losing himself in his Bach or his Beethoven (a religious four or five hours every morning just to keep the music alive within him), or fashioning tunes of his very own for an album called Kafka. That was a surprise. Kennedy said it was about change (presumably that's change as in Kafka's short story about a young man who goes to bed human and wakes up an insect - a not altogether wise analogy given the number of musical establishment figures who have lined up to take a swat at Kennedy). But, actually, it was about having changed, it was about taking stock of music's most enduring principle. It was about melody - sweet, homespun, melody. And it said more about the mellowing of Nigel Kennedy than anyone at the time seemed to realise.

But back to the here and now. He's out of purdah, he's turned 40, become a dad, and notched up his first retirement. So the artful dodger of classical music is no more. This is the second coming. He's changed, have you? Not exactly. Concert dates from Birmingham to Basingstoke are still selling faster than any at the peak of his media blitz. It's as if he has never been away. Or, perhaps, because he's been away. Everybody loves a comeback. And to come back with Elgar. Why, he even prompted a Times editorial. Hong Kong may have gone east, but Kennedy was playing Elgar so the Empire was still intact.

Actually, the choice of Elgar for his first classical recording in five years effectively brings his mature career full circle. His debut recording - back in 1984 - was of this very work. And it was as significant in its way as his teacher and mentor, Yehudi Menuhin's, classic 1932 recording (same record company) under the composer's baton. Menuhin was 14 at the time, Kennedy rather older at 28 when he set down his account. Comparisons were inevitable but redundant. Kennedy's reading was as brave, as far- reaching, as much his own as Menuhin's had been his. Those who already had him stepping into Menuhin's shoes, those (including Menuhin himself) who regarded him as a natural successor, torch-bearer of the Menuhin tradition, had seriously underestimated him. Kennedy was no one's clone, no one's successor, he was no one's fool but his own.

People often ask who Nigel Kennedy really is. They wonder about the image, the personality, the accent, the jargon. Are any of them for real, they ask? And it's true, the quirkiness of his character has come to border on self-parody. But it is real, all of it, as much a part of his persona as the instincts which make him a great player. He's the first to admit that he's stubborn, wilful, contrary, that he has a problem with authority, that he likes "to arse about". But he's serious and he's thoughtful, too. And infuriatingly loveable. "I think you grow within yourself even if you never grow up," he says, in one of those revealing moments that seem to put all the jive-talking in perspective. The fact is, he never has grown up. He's working on being the oldest football hooligan on the planet. But when he picks up that violin...

Sir Simon Rattle, his collaborator on the Elgar, decided quite early on in their working relationship (they recorded the Sibelius Concerto together some years ago) that "to know who Nigel is, you have to listen to him playing - and look at his eyes while he's playing... " He has an advantage there, of course, being close enough to the source of the sound to feel the energy, determination, defiance of the playing. But also its modesty, its inwardness. Listening to Kennedy play the accompanied cadenza of the Elgar is as much an invasion of his privacy as it is Elgar's. This is where we came in: the moment of Elgar's unmasking, three or four minutes of music that reveal more of his many-faceted personality than almost anything else in his output. Kennedy calls it the "private and personal shit" and assumes responsibility for it as surely as if it were his own. Composer and soloist are suddenly indistinguishable.

Rattle has his own theory on this one. If Elgar had been born Austrian, he'd have been Mahler, he says. "There are these absolutely volcanic emotions, and they're all the more overwhelming for being hidden beneath this fine, upstanding, frightfully English reserve. Elgar was not at all how he looked or how he acted. That was an invention. He was somebody caught in the crippling class structure of the time, somebody trying hard to be someone he was not. Talk about an assumed personality... "

Suddenly, it hits you that Rattle is talking about Kennedy. At least that's the implication. And it makes you think. Kennedy, for his part, is out of it, lost in the business of recapturing Elgar's past. Rattle truly believes that this reading of the cadenza has never been equalled: "He gets somewhere in it that very few ever reach. It's so personal, so knowingly characterised as to make you think that all the other "end of the Empire" stuff is in inverted commas... It's partly this very special variety of sound that Nigel has always found. Particularly in the quieter dynamics. Even when I've heard him playing Jimi Hendrix with his fiddle wired up, there's still the sound of a great violinist."

Not Kennedy - though, by all accounts, the first rehearsals for the Elgar found him uncharacteristically nervy. Egos were under threat, defences were up. Both parties knew what needed to be done, but were not yet of one mind and spirit as to how they might do it. In retrospect, Kennedy thinks that those initial frictions proved productive not obstructive, giving the performance and subsequent recording an edge it might not otherwise have had. Rattle is more subtly discursive: "The problem as always with music is that notation is so inexact. So two people can come to the score believing that they are doing exactly as the score says and still come to very different conclusions. I think what's interesting here is the journey we've both taken to join hands on it. I mean, this is a piece of extremes, but not extreme gestures - which is a very different thing. It has a yen, if you like, for the rhapsodic, but as always with Elgar there's this fantastic discipline at work just beneath the surface. So it's a fight between the microstructures and the macrostructures really."

Kennedy can relate to that. He's a stickler for what he calls "the big picture". "Look, man, if you buy into a strong superstructure then you also buy into the freedom to enjoy the details moment by moment. And the way you work those details, the way you pace the rhythm and shape and inflect certain phrases - that's what gives the performance a life, that's what gives it its spontaneity." In other words, freedom with purpose. The age-old witchcraft of improvisation. Small wonder many of the names in Kennedy's pantheon are jazz musicians.

So, out of interest, had he been back to listen to his old recording of the Elgar? "No, man, I'm already thinking of this one as the old recording! Once you've captured a moment, there'll always be something new opening up." The "something new" that opened up in Birmingham was, in fact, a radical advance on what had gone before. It didn't come as a surprise to learn that Kennedy had revisited Albert Sammons's old recording (the very first) with Sir Henry Wood to remind himself of its "stunning honesty". Between the grandeur and impulse and repose of the concerto, the public pomp and private circumstance, there is absolutely nowhere to hide. Spurred on by Sammons's great example (the concerto was in fact written for Fritz Kreisler, but Sammons's reading is generally considered to be closer to Elgar's ideal than any other), Kennedy was taking greater risks than ever before. By the end of the first morning's session, record producer David Groves had a complete take of the first movement that EMI could happily have issued "as is" and shamed no one. By the close of the second afternoon, Kennedy had "sorted out a few of those runs, man", and he and Rattle were no longer working the piece, it was working them.

No mention of Menuhin's recordings from Menuhin's most famous pupil, note. It's still a sensitive area for Kennedy. He graduated from the Menuhin School, but, for years, he was its personal property. And that wasn't part of the deal: "When I graduated, there was a lot of pressure on me, particularly in works like the Elgar that were closely associated with Menuhin, to carry his musical principles forward - as in imitating his way of doing things. And I was picking up mannerisms which, actually, weren't a lot to do with me. And I felt that if people were coming to make music with me, or coming to hear me make music, then I had to be a little more honest and true to myself and relate the material directly, not through someone else's rose- tinted spectacles. It was important to me that I find my own way to the Elgar. And, in that respect, I had to make a conscious effort to unlearn a lot of what Menuhin had taught me. You know, Yehudi's a really generous and wonderful musician, but I started to detect a slight disappointment in him when I wasn't doing things his way, which meant that I had to reinforce my own view even more strongly to get behind the way I felt about the music. The good things about Yehudi's training would instinctively come out in my playing, anyway, but I needed to be me if I was to be anything at all." And maybe, just maybe, the "me" he now is, is precisely the "me" that Menuhin didn't want him to be. Pause for thought. Discuss.

Kennedy feels a lot freer and in control now. His professional life pre- retirement was one long circuit of concerto playing and it felt "too transient". No creative continuity. So he's striving for a healthier mix of concerto, chamber and recital engagements. He'd like to bring the kind of telepathic rapport he has enjoyed with his closest musical associates to his concerto work. And that means cultivating new partnerships and insisting on the time for them to grow.

But right now he has some unfinished business. A few days ago, he and Rattle were striving to make music. Now they were. And in that strangely consoling heartland of our culture called "English pastoral" Vaughan Williams's The Lark Ascending seemed all too appropriate. Kennedy was now way above the clouds and not about to touch down. Yogic flying? I guess Nigel Kennedy plays the Elgar Violin Concerto with the LPO, conducted by Roger Norrington, at the Royal Festival Hall, London SE1, on 8 October. Kennedy and Rattle's recording of the concerto will be released on EMI Classics in November