It would be fascinating to ask top musicians to vote on the conductor they most admire. My hunch is that the winner by some distance would be the man sitting opposite me in a Munich restaurant. In a few hours Mariss Jansons will power and beguile the Bavarian Radio Symphony Orchestra through an epic programme of Brahms and Mahler.

The 63-year-old Latvian will end the concert, as usual, ashen-faced with exhaustion. His father died immediately after conducting a concert. Jansons himself had a massive heart attack while conducting La Bohème (typically, he was still trying to beat time as he dropped to the floor). It took him two years to recover. So the warning signs are there, as his doctors and wife never stop reminding him. But they have more chance of persuading a brass section to turn teetotal than getting Jansons to ease off.

Right now, though, the maestro is troubled. About the state of the world. “People have no spiritual values. It’s money, money, money.” About declining audiences. “Five years ago you couldn’t get a ticket for the Metropolitan Opera. Now? Easily.”

And about Russia, his spiritual home (he was raised in St Petersburg), where his daughter is now a rehearsal pianist at the Maryinsky, and where he still keeps his massive collection of scores. “Russia is dead from corruption,” he says. “Most of the richest people there should be in prison.”

Surely, I say, you don’t want the communists back. “No, but I would like to bring back some aspects of that time,” Jansons replies. “There was comradeship then. People took care of neighbours.”

Jansons isn’t really grumpy. He brims with an all-consuming passion for life and music, and gets cross only when others don’t share that. As in his wretched visit to Glasgow last season, when terrible marketing meant that the world’s most revered conductor was playing to a half-empty hall. “Very disappointing. I hate not having a full house. It’s bad for me psychologically, and bad for the orchestra financially.”

But he gets just as cross when orchestras don’t share his fervour for music. In fact, he no longer works with those that don’t. “Berlin, Vienna, the Concertgebouw in Amsterdam and the Bavarians: these are the best,” he declares. “And I don’t say that because I happen to be the conductor of two of them. I try to be objective. They are full of players who say: ‘I give my life to music’. That is not so common, I think.”

Indeed not. But in bracketing the Bavarians with those other three illustrious bands, is Jansons being entirely objective? After all, his decision four years ago to quit Pittsburgh (he hates jet-lag and isn’t all that fond of America) and become principal conductor in Munich was a shock. And his subsequent decision to accept exactly the same job with the much more famous Concertgebouw has made life awkward. “For months I was in emotional distress,” he says. “I agreed to take the Bavarian job. Then Amsterdam approached me. Can you imagine the dilemma: being offered such quality, that wonderful hall, and the prestige? How could I say no?” Quite. It must have been a bit like getting a call from Manchester United just after signing for Charlton Athletic. But how does Jansons resolve the clashes of loyalty? “Friends in London and New York said to me: ‘Don’t worry, our cities have two concert halls. You can tour with one orchestra to one hall, and the other to the other’. ”

And repertoire clashes? “Jansons is now a split personality: 50 per cent Amsterdam, 50 per cent Munich. I completely ignore my own wishes. I do whatever each orchestra needs. Thank God I have a big repertoire — and please, do not think me arrogant for saying that. During those years in Oslo and Pittsburgh I really did everything.”

But what of the perception of a quality gap between Amsterdam and Munich? Jansons doesn’t admit to any such thing, of course. But he then spends half an hour telling me of his efforts to attract top players to Bavaria. “It isn’t easy. People say ‘you take so long to fill vacancies’. But I want the best. I have just appointed a principal cellist, very young, fantastic. Also first trombone, timpanist, double-bass principal — all wonderful. But some vacancies we haven’t filled. We pay good money, far better than at the Concertgebouw, where the young players can’t even afford to live in Amsterdam. But if you take players who are only attracted by the money, it’s like an illness, a bacteria that spreads round the orchestra.”

I have no doubt that Jansons will soon haul the Bavarians to the top of the tree. He’s not a tyrant like Toscanini, but he’s no less of a perfectionist. He has already installed the Bavarians as resident orchestra at the Lucerne Easter Festival (opening tomorrow), and talks of rivalling Salzburg’s tired Easter Festival with a mixture of big-name singers and choral epics.

And then? “There is an old saying: great hall makes great orchestra.” Meaning that he won’t rest until Munich builds its own Concertgebouw or Musikverein? “Well, you know what Lenny Bernstein said when they asked him how to improve the present hall? Burn it!”

Details of the Lucerne Easter Festival (April 1-9) on www.lucernefestival.ch