I don’t write many fan letters and this is the first I have written to a dead person. But you are not dead, of course, in any significant sense. Though you’re 100 years old this month and your bones rest in a place secure from the Politburo, the Comintern, the KGB and the rest of the jackals who failed for half a century to wrestle you into submission, the personality, the essence, the magic called “Shostakovich” is more alive today than ever.

I’m writing because I want to say how much your work means to me.

As a film critic I have no business trespassing into other bailiwicks – and may risk getting shot as a trespasser by concert-reviewing colleagues – but sometimes a passion is a passion. When an artist’s centenary meets an admirer’s bursting stockpile of the unsaid, critical mass is reached.

Music is the art without frontiers. I don’t mean between countries – or even critics – but between the conscious and unconscious mind, perhaps between death and life. Does any other art call out from the dead like music?

When you yourself turned these lines of poetry by Michelangelo to song in 1974 – “I am not dead; although buried in the earth, I live on in you, whose lamentations I can hear, since friend is reflected in friend” – you gave them a resonance they would never have on the page alone. Music, for reasons we still don’t understand, makes everything permeable. It breaks the seals in our souls. It touches the finite and makes it infinite. In your case, it outwitted and has outlasted an entire empire of evil, repression and termination.

Have you any idea how many concerts have been devoted to you in this centenary year? Let’s just call it a million. I have been to several. I think my nearly insane love of your music started when I saw Lady Macbeth of Mtsensk at London’s Royal Opera. No one had warned me this was a work of blistering beauty; that it mixed psychological realism, wild tonalities and jet-black satire in a way that makes it a companion in Hell with Lulu. It bristles with genius; sets one’s hair on end; pings, soars and screams.

Why did it home in on my DNA, this score that can leave some music-lovers untouched and unscorched? Maybe because I was a postwar child, born in 1947, and historical trauma was in my genes. Music from the 20th century’s first half, when the birth of artistic discord matched the swell of the world’s disharmonies, has always had for me an unbidden voluptuousness.

Lady Macbeth of Mtsensk was a turning point in your life. It earned the famous fury of Joseph Stalin. Like most political dictators, Stalin was a philistine for whom artistic adventure was a crime of anarchy, and a paranoiac who believed that every peel of mockery was aimed at him. So after walking out of your opera in 1936 he ordered Pravda, the state newspaper, to condemn the work as “chaos instead of music”, “din, gnash and screech” and “cacophony”. (This was 30 years after atonal music actually came into being. Thank God that Berg and Schoenberg did not live in Russia).

Your opera career never looked forward again. Your creative being rocked under the impact. You hid your work-in-progress Fourth Symphony in a drawer – that piece of enraptured violence, that love-hate hymn to modernity with its clanking pistons, screeching whistles, brute marches and skeletal elegies like ghosts adrift in a graveyard – and gave Russia and the world the well-behaved Fifth Symphony.

You called it “an artist’s practical response to just criticism”. It had tunes. It had structure (four movements). It had patriotism, or seemed to. In short it had Stalin appeal.

What on earth were you up to? Were you as innocent as a fox? Were you cleverer than anyone knew? Or, helped by some unknown muse, did you just get brilliantly lucky?

For this, of all unlikely moments in your career, when lackeyism could have sunk you into Lethe, when compromise could have rotted your reputation and self-belief, was when the world fell in love with you. It has never fallen out.

The Fifth Symphony was a compromise that didn’t compromise. It was a squared circle. It was genius with a welcome mat. It made the Soviet state pigs feel they could wipe their trotters at the entrance and hand you their hats. Yet it was still a work of genius. Today the symphony is just as interpretable as a cry of grief and wrath over Soviet Russia as an endorsement of Stalin.

You carried on, avoiding the gulags, smuggling impertinences into your music (the Sixth Symphony) and writing string quartets as private therapy. Meanwhile friends and fellow artists were being dragged to Siberia, shoved in the Ljubjanka, or otherwise stiffed or silenced. You dreaded the knock on the door.

We who live in countries where a knock on the door means only a neighbour seeking a lost cat, or at worst a Jehovah’s Witness, cannot understand the teeth-chattering anxiety you must have felt day by day, week by week, year by year.

A bully state loves to rid itself of artists. Rome exiled Ovid, Spain silenced Lorca. These voices commit the worst crime of all: expressing the inexpressible.

In Russia the famous theatre director Meyerhold was arrested and his wife murdered. Prokofiev was forced to compose songs to Stalin and Lenin. Soon you were fired from your teaching posts and earned money by composing film music. (Here’s a confession. I have no interest at all in your film music despite being a film critic. Perhaps I feel you shouldn’t have been wasting your time – or that the state shouldn’t have been wasting it for you.)

What did you think and feel back then? Can you remember? Do you want to? The 1940s in the USSR were not a pretty time. An artist who survived them becomes, to modern minds, a little suspect. Did you feel the way the survivor of a disaster is said to feel – grateful but culpable, as if responsible for the deaths around you? Though you won almost every personal face-off with fate you seem never to have felt triumphal. Nor even secure.

You must sometimes have believed you were the composer least likely to be feted by after-generations. In many ways you are an unlikely candidate for popularity. You do not have star quality in photographs. Your thin lips, goggle glasses and sparkle-free stare, atop the duty jacket and tie, suggest an embalmed sixth-former. You seem impassive even when wearing a fireman’s helmet and pointing a hose in that famous shot taken during the bombardment of Leningrad. Can humanity inhabit so forbidding a phiz?

Let a person just turn on your records. From the first notes of a Shostakovich composition – almost any of them – we are in a sound-world 20,000 leagues deeper than any other Russian’s and more beautiful. The swirling, searching, unmelodic beginnings draw us in, separating all the bits of our brains that need separating. Then, over an hour or so, the bits are drawn together again. This is what great art does. The artist takes the viewer/listener apart in all his component pieces. Then he puts them together again, so the person is a more fully functioning human being.

I love the way themes and melodies in your music go through changes as intricate yet organic as the seasons. This can be so subtle that some performances don’t “get” them at all.

I cherish the memory of a visit to the Naples Philharmonic – that’s Naples, Florida – when for some mad, bold reason this town nestling between the Everglades and the Gulf of Mexico, and counting retired dentists and ageing golden girls as its main population, performed your Eighth Symphony. Your Eighth! Pain, tragedy, dissonance, the whole thing.

But the Naples Philharmonic played it fit to bust, even after half the audience left in the interval because they had only come for the Mozart. The orchestra played the third movement, or second scherzo, as it should be played, like a train running one over. (Aren’t those screaming whistles to die for?)

But the Naples Philharmonic missed the final turn to winter. Bernard Haitink caught it the following summer at the Proms in London. The last ear-bashing dissonance, in the last movement, should turn all the juvescent tenderness of those little melodic shoots to a post-nuclear chill. When the music goes quiet for the last time, we should hear the landscape whiting out. We should hear the “ping” of frost and freeze. Great tragedy in the quietest of things.

I said your music went deeper than any other 20th-century Russian’s and it does. This is hard on Prokofiev, your nearest peer. He went through the same horrors as you. He even came back to Russia from expatriate freedom to be put through them. But playing his music after yours is like drinking sherry after Scotch.

We don’t want a programme – and frankly your programme symphonies are your worst (movie music again) – but what are Prokofiev’s symphonies and concerti “about”? Nothing, really. They are just about their own clever, gorgeous, vibrant, inventive music-making.

As for Stravinsky, words cannot do justice to my aversion. Stravinsky fled Russia to become a dilettante for all seasons and a servant to all masters. His modernism wears the label, “Like me, please!” He turns everything, from politics to war to religion, into pabulum for his easy-listening modernism or neoclassical potboilers. The sparkling surfaces are never compromised by depth. The Rite of Spring is the work of a stockbroker donning a grass skirt to have a good time at a luau.

(Stravinsky had the nerve to say that you, Dmitri Dmitrievich, developed disappointingly after the promise of your First Symphony. What he meant was that you did not turn into a pan-global popinjay like him.) Do you see my point? You and your music set out to ingratiate no one. I except those coerced capitulations to Stalinism. But even here – let’s say it again – you capitulated with a clenched fist and mendacious smile. Sometimes that was not possible: for instance after the culture commissar Andrei Zhdanov’s 1948 denunciation of Soviet music’s “formalist cosmopolitan tendencies” (totalitarian condemnation has a Dadaist vernacular all its own). And so you bent the knee until it was safe to straighten it again.

You composed your 12th Symphony – bombastic but beautiful in bits – and music for hagiographic films with forgotten titles . . . Let’s Love Stalin, I Lost My Heart at the Finland Station, Carry On Comintern, whatever.

Meanwhile your Fourth Symphony and First Violin Concerto lay in a drawer – I like to think it was the same drawer, a bed of sin for cohabiting outlaws – until they could be played after Stalin’s death. Your 10th Symphony let out all your pent-in rage and grief as soon as Stalin had died. (Poor Prokofiev. He died the same day and lost all the obituary space. He deserved better.)

After that, as many great artists do, you seemed to fall in love with death. Your 14th Symphony was a vocal work set to poems about death by Apollinaire, Lorca and others. It had a small orchestra and a quality of entranced obsession. It gave the dangerous sense that it was putting a would-be suicide’s gun into the listener’s hand and saying, “Go, thou, and do likewise.”

But no. Even at this time you loved life, not death. It was just – wasn’t it? – that life had become attenuated, hypersensitive. Your string quartets got odder and sparer till they were almost as out of reach to human ears as a dog whistle. The movements of the 15th, final string quartet are all marked adagio, except for the last, which is marked molto adagio. How’s that for minimalist chutzpah?

This raises an important question for those interested in your work. Did you have a sense of humour? Frankly I don’t think you did. (Contradict me if you disagree.) I know you wrote uproarious passages. You could be searingly satirical: the burlesque Keystone Kops-style music in Lady Macbeth of Mtsensk; the Sixth Symphony’s presto; the William Tell quotes and other prankish plagiarisms in the 15th Symphony. But for me they are not mirthful, more the manic side of manic depressive, and twinned to the passionate indignation of those spoof-militaristic scherzos you kept turning out.

Why does this question occupy me? Because the lack of humour was nothing to do with you, I believe, but with your situation. It demands the follow-up question: can anyone have a sense of humour in a totalitarian state?

Humour is the licence to be irresponsible. It can only breathe and live in an oxygen of impunity. In a dictatorship humour becomes something else: a mocking desperation, a hysterical or derisive scorn. Wit as surgery. Even wit as martyrdom: “I’ll die laughing.” So you spent your life in an oscillation between the gay and the grave, with the gay often wearing the garments of the grave while the grave had its consoling, finite gaieties.

What an unwitting clairvoyant you were. Isn’t the whole world like that today? On Planet Earth in 2006 the only people left believing in a literal afterlife – a possibility you repudiated in the 14th Symphony (as if to say, with Buñuel, “Thank God I am still an atheist”) – are the terrorists who want to blow us all up and retire to their virgins in the sky. That crew forever suckling on their murderous mysticisms. The rest of us have downgraded Heaven to a metaphor, the first step to downgrading it to nothing.

You saw that the only religions worth a person’s worship are freedom and, if it can be lived with honour, life. Death in the service of anti-totalitarianism was a noble heroism: witness the millions of Russians who chose it or had it chosen for them, becoming the known and unknown soldiers of modern history’s first, true war on terror.

But you decided to live, striving to limit your capitulations to superficial ones. That way, a man gets the span of life he didn’t ask for but has every right to keep. And he might, if he is a genius, leave something behind to strengthen and reassure those who come after him.

Your music expresses the doubts and certainties of what you thought and did. It amplified your thoughts, fears, nightmares, dreams; it showed they are, essentially, those of all of us. You glamorised nothing but gave a fierce beauty to everything.

I think your brand of heroism, obduracy, belief and self-belief need saluting. I do so on behalf of as many people as will let me represent them here. For the rest of my life, like millions of humans at this earthly time, I shall only have to hear your sad, lyrical, anguished music to say to myself: “They’re playing our tune.”