Backstage at the Concertgebouw in Amsterdam, one of Europe's most famous concert halls, Mariss Jansons is reflecting on his latest performance. He has just conducted his Royal Concertgebouw Orchestra in a scintillating programme of Berlioz, Debussy, Berio and Ravel - one of two concerts they will play at London's Barbican this weekend - but, a lifelong perfectionist, he is not completely happy, and is talking things over with a committee from the orchestra. When I'm finally allowed through to the conductor's dressing room to meet him - a place where everyone from Gustav Mahler to Leonard Bernstein has taken up residence - he explains. "This is the third time we do this programme. I must say that these Sunday midday concerts are not easy to do. Psychologically, physically the energy is difficult.
"I prefer evening concerts. But you know maybe, because it was the third time, there was room for some improvisation and in Debussy's La Mer, we got a very transparent, very nice sound, and in Ravel's La Valse as well. But I think the second evening was perhaps the best."
I trust his assessment of his afternoon's work, but it is hard to imagine how the concert I've just heard could have been improved upon. It's my first time in the Concertgebouw. By reputation, this is one of the world's greatest acoustics for orchestral music. All I can say is that I've never heard an orchestra sound as thrillingly clear or as overwhelmingly sensual as it does here: the delicate splashes of the percussion writing in La Mer were shimmeringly evocative, the huge climaxes of La Valse massively powerful.
But acoustics are meaningless without the virtuosity of the performers, and Jansons moulded the opulent warmth of the Concertgebouw's string section and its dazzling woodwind players into a compelling whole. La Mer was not just an impressionistic illustration of the sea, but a physical experience in its own right, an ocean of sound that contained everything from limpid tranquillity to vicious storms; La Valse a devastating dramatisation of the moment when the pleasure of sensual abandon, the voluptuous rhythm of the waltz, curdles into decadent over-indulgence.
For all his brilliance at the helm, Jansons can't take the credit for turning the Concertgebouw into a world-class band: since its formation in 1888, the orchestra has been recognised as one of the world's best. Jansons is, however, only the sixth man in charge of the ensemble, taking over from Italian Riccardo Chailly in 2004. I ask him about his vision for the future. "I just want to continue the growth of this wonderful orchestra, and to play a repertoire that goes from Haydn up to contemporary composers. But, you know, even if it's a top-class orchestra, nothing comes by itself. You must always work to get the best results. Talent is one thing, but work is work - always work."
Jansons, who has just turned 64, should know. He is a product of one the most intense musical educations anywhere in the world. Born in Latvia, where his father was conductor of the opera house in Riga, the family moved to Leningrad when he was in his early teens and Jansons enrolled on the legendary conducting course at the Leningrad Conservatoire. "It was the best training in the world for conductors. We had fantastic opportunities because there was a professional orchestra in the conservatory that we could conduct, and an opera house, too. Such a unique thing doesn't happen any more."
But conducting was in Jansons' musical make-up right from the start. His father was a role model, and conducting was a dream that the young boy played out in childhood games and fantasies. "It started when I was four or five," he says. "I made an orchestra of buttons, of paperclips, and rubber erasers - thousands of things - and I would conduct concerts."
Jansons would lay out this miniature orchestra in minute detail, with different formations for different repertoire, and conduct whole pieces from full scores. "If my mother changed one piece for another, I could recognise immediately what had been altered, that there was a button - a player - in the wrong place! I would design whole programmes, and conduct them in rehearsals, after which I would clear them away, and then they would come back for the concert." Jansons would even dress up in different concert outfits, depending on whether it was a matinee or evening gig. "I played this game for a very long time. Until I was 14 or 15."
It's a passion that led him - after the transition from buttons to flesh-and-blood players - to long associations with the St Petersburg Philharmonic, where he was involved for 30 years, a two-decade stint transforming the Oslo Philharmonic from also-rans to world-beaters, and later pulling off a similar trick with the Pittsburgh Symphony in the US.
Today, the Concertgebouw isn't Jansons' only job: he's also music director of the Bavarian Radio Symphony Orchestra in Munich. While the Bavarians are not in the same league as the Concertgebouw in terms of fame or prestige, they are a force to be reckoned with, as Jansons showed at the Proms a couple of years ago. During a performance of Strauss's Ein Heldenleben, the lights in the Albert Hall went out, but Jansons and the orchestra simply kept playing from memory until they were turned on again.
How on earth does he manage these two demanding positions in Holland and Germany? "I must treat them both equally. I always say that I've divided myself into two Jansons: 100% Jansons in Amsterdam and 100% Jansons in Munich. I have to be very objective, and not prioritise one over the other."
He would say that, of course, but this musical multi-tasking can lead to problems: "I have to be careful about tours, not to play the same piece in the same city with the different orchestras." It's a headache, too, for orchestra managers and tour promoters, all of whom want as much as they can get from him. And the endless round of international travel leaves its mark on Jansons' personal life. His constant companion is his wife Irina, who has devoted her life to accompanying him at every rehearsal and concert. They don't have a base in Amsterdam, living instead in hotels for the 12 weeks of the year they are in Holland, and their home is still St Petersburg.
"I don't perform at all there any more," says the conductor. "So between tours, I go to St Petersburg and feel at home. I read, I prepare scores, but I'm not doing anything else there. You need somewhere to have some kind of rest in your life."
He doesn't take holidays, either. Last year, he squeezed in some time in Mauritius after a gruelling tour of Japan and Taiwan with the Concertgebouw. But this week in the sun turned into a chance to catch up on work: "I was working on Beethoven's Ninth, so every day I was with the score on the beach."
Jansons lives his life with the same intensity that defines any of his performances. But he is lucky to be able to live it in the way he does. Eleven years ago, conducting Puccini's La Bohème in Oslo, Jansons had a heart attack on the podium, just before the end of the piece. He says he knew what was happening to him - his father collapsed and died while conducting a concert with the Hallé Orchestra - but still felt he could get to the end of the opera. As he collapsed, he was still beating time. Now fitted with a defibrillator to prevent heart attacks in the future, he says it's an experience that changed his approach to music and to life. "You know, when you face such a dramatic moment in your life, it influences you - not consciously, but sub-consciously.
"I think you become a more profound person. I felt that I started to like more quiet music, definitely; I started to enjoy performing more profound music, more slow tempos. But you have to forget about it as well - you can't always think about that experience, even if, from a medical point of view, you must never forget."
He admits to not always being as careful with his health now as he was in the immediate aftermath of his operation: Irina offers me a sumptuous selection from Jansons' favourite chocolates - ironically called Puccini - before I leave.
Jansons' life now looks like the charmed life of the maestro, able to pick and choose his programmes, his soloists, and his orchestras: every concert he gives with the London Symphony Orchestra is a highlight, and it's the same with the Vienna Philharmonic. But he still has unrequited musical passions. "I want to do opera, more opera. My problem is that I don't have the time. But I grew up in the opera house, and my biggest passion is opera.
"I'm so happy with the Concertgebouw because I get to do opera every couple of years - it's Carmen next. But this is my problem: I really want to do more." I put it to him that there's a simple solution: give up one of his orchestras. He looks pained, and says, "it's good to have dreams, and if you don't fulfil them, it's OK; hopefully, you can in your next life. In my next life, I'd like to do only opera." In this life, for the moment at least, the opera world's loss is the concert hall's gain.
· Poulenc's Gloria and Honegger's Symphonie Liturgique, conducted by Mariss Jansons, is out now on RCO Live; a 14-CD box set, Anthology of the Royal Concertgebouw Orchestra, is released next month. Mariss Jansons conducts the Royal Concertgebouw Orchestra at the Barbican, London EC2 tomorrow and Sunday. Box office: 020-7638 8891
