Who would have thought that making a film about Tchaikovsky would have led to detailed research into the history of barrel organs? But a crucial moment in the composer's childhood is connected with an orchestrion that his family owned and which introduced the young Pyotr Ilyich to the music of Mozart - a love and inspiration to him throughout his life. So I began the search for a working example of the sort of orchestrion the family might have had in the 1840s.

They do have an instrument on display in the house (now a museum) in Votkinsk where Tchaikovsky was born, but they obviously didn't do too much research, since it plays a paper roll - a system that wasn't invented until about 1900. Luckily, thanks to invaluable help from Arthur Ord-Hume, the world expert on barrel organs, we tracked down a suitable orchestrion playing massive spiked barrels in a private collection in Devon. This is just the sort of instrument that papa Tchaikovsky would have bought for the family home and a glorious thing it is too.

In fact, Saturday's instalment in BBC2's Great Composers series will be the first time that Tchaikovsky's birthplace will have been shown internationally on film. The composer's father ran one of Russia's leading steel works; more recently, it manufactured Russia's SS20 nuclear missiles. As a result, Votkinsk was off-limits to foreigners until 1990. I suspect this strange irony of history is one reason why most biographies of the composer misleadingly cite his father's profession as "mining engineer".

An enormous amount of similar misinformation, speculation and myth has fed our image of Tchaikovsky as a gay, mad Russian perennially poised on the verge of a nervous breakdown. And the biggest of these myths surrounds his death.

When Tchaikovsky died on 25 October 1893, after a four-day illness, it was chronicled in the medical records and reported in the newspapers as a case of cholera. Today, though, it has become almost universally accepted that he committed suicide. I can't claim an unequivocal answer to this but, as Alexander Poznansky's recently published Tchaikovsky's Last Days points out, there is no real evidence for suicide, while the composer's illness and death are among the best-documented in history.

The most popular suicide story has the composer hauled up before a Court of Honour composed of old schoolfellows and ordered to poison himself so as to prevent scandal about his homosexual activities bringing the School of Jurisprudence into disrepute. Yet this ignores the fact that the School of Jurisprudence already had a notorious reputation for homosexuality; that two of Tchaikovsky's old schoolmates were openly homosexual; that, although technically illegal since 1832, there is not a single known prosecution for homosexuality among the well-to-do of 19th-century Russia; that the Grand Duke, the Tsar's brother, was well known to have the same inclinations; and that Prince Vladimir Meshchersky, one of the most flamboyant of homosexuals, was protected by the Tsar himself when he ran into scandals.

It's easy to think that Imperial Russia must have been more repressive than Victorian England, but the Petersburg press was horrified when Oscar Wilde was convicted just two years after Tchaikovsky's death. How could the authorities imprison a great artist for being homosexual? On a more practical level, if you examine the well-documented movements of the composer in the last week of his life, there isn't the time for the Court of Honour to have taken place.

Setting the Court of Honour aside, others argue that Tchaikovsky could have poisoned himself because he was uneasy about his homosexuality or because of unrequited love for his nephew Bob Davidov, to whom he dedicated his last symphony. But I think the composer's letters and diaries suggest the opposite - that he had grown to accept his sexuality after the fiasco of his marriage in 1877 and that the last weeks of his life were full of plans for new works and concert tours.

It is much more likely that Tchaikovsky did drink cholera-infected water during his last stay in St Petersburg - and, given the incubation period, it was probably before the dinner in Leiner's Restaurant at which he is supposed to have drunk the fatal glass. Significantly, an official inquiry into the water supplied in the capital's restaurants - an inquiry instituted as a direct result of Tchaikovsky's death - revealed that they all mixed boiled and un-boiled drinking water, so the composer could have become infected at virtually any time. What's more, he had a history of stomach problems and had been treated for a mild form of cholera only a few months earlier.

So, if the evidence for a natural death is so conclusive, why the persistent tales of suicide? I put it down to the power of the Pathetique, Tchaikovsky's last symphony, which he conducted just nine days before he died. The composer never disclosed specifically what the piece was about, but there's no doubt it is concerned chiefly with death. The first movement is dark, at times violently turbulent, and quotes a Russian Orthodox funeral chant. The last movement, unprecedentedly, is a tragic slow finale, dying away to nothing. When Tchaikovsky conducted it on 16 October in St Petersburg's Philharmonic Hall, he was greeted with tumultuous applause, but his work was met with reserve and bewilderment. When it was repeated on 6 November, however, with the city still reeling from shock at his sudden death, the undeniable power of the music was given a meaning it was never intended to posses. For here was Tchaikovsky quoting the very funeral chant that was sung over his body at his state funeral in Kazan Cathedral. The symphony must have sounded like the longest suicide note in history. Given all of which, it is easy to forget that Tchaikovsky had finished the Pathetique six months before and had completed several other, not particularly tragic, pieces in the meantime.

To me, the suicide story has a powerful dramatic and emotional truth, but little likelihood in reality. One reason it has taken such a hold is surely because Tchaikovsky's homosexuality was virtually a taboo subject in Soviet Russia. Now at long last Russian scholars and biographers can be open and frank about all aspects of Tchaikovsky's life. Much has been published that was previously censored and there's more to come. For the first time, we can get a true picture of the composer's sexuality. He had a long relationship with his manservant Alyosha, frequently had affairs with members of the lower classes, and also used male prostitutes, particularly abroad. But he also had strong platonic attachments to younger men - most importantly, his nephew Bob Davidov and the violinist Yosif Kotek, who inspired Tchaikovsky's lyrical Violin Concerto.

In a previously censored letter to his brother Modest, Tchaikovsky describes his feelings for the 22- year-old violinist: "I have known him for six years already and have several times fallen in love with him a little... However, I am far from wanting physical relations... It was a ravishing moonlit night. I hired a troika and we flew... He was feeling the cold in the end of his nose. With my bare hand I held up the collar of his coat to warm this nose that was sacred to me. The freezing of my hand gave me pain along with the sweetest consciousness that I was suffering for him. We spoke about the concerto... and he repeated he'd get angry if I didn't write it."

When you know the feelings behind the concerto, I think you hear it in a new light - particularly as we were lucky enough to get Maxim Vengerov to perform it for the film. Not only is he the greatest violinist playing the concerto today, but he is the same age as the young Kotek who so transfixed Tchaikovsky.

'Great Composers: Tchaikovsky': 8pm Saturday on BBC2

Simon Broughton, director of a new BBC2 documentary about Tchaikovsky, dispels some of the myths that still surround Russia's favourite composer.

The man and the myths: five things you thought you knew about Tchaikovsky

1 He committed suicide by taking arsenic to avoid a homosexual scandal. Highly unlikely (see main article).

2 He had passionate sex with his wife (memorably played by Glenda Jackson, our current Minister of Transport, in the Ken Russell film, right) in a train carriage after their wedding. But on that journey to St Petersburg he could hardly bear to talk to her. His homosexual friend Prince Meshchersky had burst into the carriage and, upon arrival in St Petersburg, the first thing the composer did was to telegraph his violinist friend Yosif Kotek.

3 Tchaikovsky's brother Modest suggested the name Pathetique for his Sixth Symphony the day after its premiere. No, Tchaikovsky had already referred to it by this name in a letter to his publisher more than a month before.

4 While composing the famous letter scene of his opera Eugene Onegin in 1877, Tchaikovsky received letters from Antonina Milyukova declaring her love for him. Fearing the unhappy events that follow the rejection of Tatyana's love letter to Onegin in Pushkin's poem, Tchaikovsky decided to marry her. A splendid example of art influencing life? Wrong, though Tchaikovsky himself was responsible for spreading this misconception when he recounted the events to his friend Nikolai Kashkin. In fact, Antonina's letters preceded Tchaikovsky's decision to write Onegin. Possibly life influencing art.

5 Tchaikovsky attempted suicide after his marriage by wading into the freezing cold Moscow River. Not proven. The only source for this is Kashkin's unreliable account written more than 40 years later.