Grand obsession

The great love of Leos Janacek's later years lit the fires of his creative passion and inspired many great works, including a mysterious song-cycle. Dennis Marks unlocks its secrets

The story has haunted me for almost 30 years. It is a tale of forbidden love and multiple deceptions, of obsession, inspiration and betrayal. It concerns a great artist, an attractive woman and a mystery that has puzzled scholars for three generations.

In 1917, the Czech composer Leos Janacek met and fell in love with a young Jewess, Kamila Stosslova. He was 63, she was 25. He was locked in a loveless marriage, she was the contented mother of two young sons. After decades of neglect, he had at last become something of a celebrity. She was the wife of an antiques dealer, living quietly in a backwater of rural Moravia.

The narrative is as old as time: the infatuation of a man in late middle-age for a vivacious young woman. So where's the mystery? What makes it remarkable is the effect this "dark-eyed gypsy" had on the white-haired composer. For the next 10 years, an unbroken stream of masterpieces poured from Janacek's pen - four operas, two string quartets, two concertos, a stirring Sinfonietta, and a mighty liturgy, almost all of them inspired by Stosslova. Most intriguing of these autumn fruits is the work he sketched a few days after the meeting, the strange, obsessive song-cycle known as the Diary of One Who Disappeared. It is a setting of verses supposedly by a young Moravian farmer, who had been seduced by a Roma girl and had run away to live with her. The poems had been published in a newspaper a year earlier and Janacek had been hoarding them, as if waiting for an excuse to set them to music.

In the composer's imagination, Stosslova, the young bourgeois mother, was reinvented as the sexually provocative Gypsy of the poems. Within days of meeting her, in the little spa town of Luhacovice, he sent her flowers and a breathlessly indiscreet letter. Under the influence of his new passion, he began to work feverishly on the songs. This brings us to the first mystery. Janacek was unaware that the poems themselves were an invention. The farmer never existed, and the verses were a fake. They were the first of many deceptions and self-deceptions woven into the final decade of Janacek's life.

I have always wanted to make a film about this most intoxicating of 20th-century composers. In the early 1990s, after the collapse of Communist Czechoslovakia, a wealth of new material began to come to light. What the film needed was a detective to piece together the fragmentary story of Janacek's Indian summer.

Five years ago, I realised I had something better - a singing detective. I had known the tenor Ian Bostridge since he had exchanged the academic life for the career of a singer. We had worked together at English National Opera, and when I returned to television, I asked him if he wanted to participate in my detective story. Not only was he intrigued by the project; he was in the middle of learning the Diary. However, his vertiginous career meant that it was three years before we were able to collaborate.

But he did have something to bring to the table. He had come across a scholar from Janacek's home town of Brno called Alena Nemcova, who had unearthed the solution to the first of the mysteries. She had found out who the writer of the verses was - a disappointed minor author by the name of Osef Kalda. In a letter to a friend, Kalda confessed to passing off his fake bucolic poems as the work of a self-taught country boy.

However, like a Russian matrioshka doll, this mystery concealed another and another. Janacek had written the first 10 songs at breakneck speed, firing off letters to his new love describing his progress. Then he stopped, halfway through the cycle, at the point where the young farmer is about to consummate his passion. He put the work aside for 18 months.

Why did the infatuated composer abandon his love gift and bury it in a chest? Why did Kamila, who was evidently indifferent to Janacek's music and devoted to her husband and children, continue to entertain Janacek's obsession for more than 10 years? Why did her husband allow the correspondence to continue? And why, in the composer's final weeks, did she agree to visit him and sleep in his country cottage?

When we visited Moravia, Ian and I began to discover that, like the story of Kalda's "sleight of hand", some of the answers had always been available. They had simply slept for 45 years in the black hole of Communist Czechoslovakia. Soviet societies were particularly sensitive to the foibles of their national heroes. More than 700 letters from Janacek to Kamila had been lying unread in private hands, but it was not until the early 1990s that the full collection was published. Janacek's wife Zdenka had written an unflattering set of memoirs of the composer, but they were left incomplete on the eve of the Second World War. Various attempts were made to reconstruct them, but again, the Communist authorities were not eager to publish.

We owe it to the tireless Janacek scholar John Tyrrell that this material has finally been made available in English. However, mysteries persist. My friends in Brno introduced me to the composer Milos Stedron and the archivist Svatava Pribanova, both of whom had unpublished information to disclose. One fascinating detail was a letter written in 1927, which Stedron saw 25 years ago, suggesting intimacy between Janacek and Kamila. But the letter has disappeared. Was this another instance of protective Socialist embarrassment on the great composer's behalf? When I was in Brno for the anniversary of Janacek's birth, there were some scholars who believed that Zdenka's memoirs should never have been published, and who resented outsiders meddling with the personal secrets of their greatest 20th-century composer.

When we met Kamila's son Otto, he gave us a very different, far from complimentary picture of Janacek and his mother's feelings for him. He also corrected a familiar myth about the reasons for Janacek's final illness. However, he was not a witness to a further mystery - the deathbed change Janacek made to his will, bequeathing a substantial slice of his royalties to Kamila. And we shall probably never know the reason for Kamila's husband allowing the liaison to continue - except, perhaps to guess that for a stateless Jew born in Lvov, it was worth indulging the fantasies of a Czech celebrity. As for the reasons for the gap in the composition of the Diary and all the other puzzles, you will have to watch BBC4 this Saturday for an answer.

How much does this matter? Milos Stedron is sceptical. "I agree with Stravinsky. Music is music," he says "and emotions are emotions." Nevertheless, he points out that Janacek almost always required "a pretext" for a new creation. The works inspired by Kamila, from Katya to From the House of the Dead, are potent witnesses to the fire she ignited. We certainly need something to explain how, in his final years, a little-known choral conductor from a province of the Habsburg Empire became one of the 20th-century's great musical dramatists.

Ian Bostridge is a scholar as well as an artist, and he is tempted to support Karel Hohnal, the custodian of Janacek's house, when he says: "Better not to comment." However, as a film-maker, I will indulge in one small speculation. Both of Janacek's children died young. His marriage to Zdenka, always uncomfortable, never recovered from the loss. In his letters to Kamila, Janacek imagined their having a child together. He bought two paintings of cherubs from her husband, which he called "our children". When he described the effect of Kamila on his compositions, he used the phrase "you are giving birth."

In the first work inspired by Kamila, she is a provocative gypsy. In the last, she has become a young Tartar boy. It was the composer who was giving birth, not the object of his infatuation. The tale of Leos Janacek and his dark-haired muse brings us to the white-hot core of inspiration itself - which is the greatest mystery of all.

Dennis Marks is a former director of ENO. 'Janacek's Gypsy Love: a musical mystery with Ian Bostridge', BBC4, 14 February at 7pm