Echoes from the city of lost children

I'm on my way to meet the Venetian writer Tiziano Scarpa at his home in the Santa Croce district of Venice.

After disembarking from the water bus, I walk past a Baroque church facing the Grand Canal, a nobleman's palace converted into a costume museum, another palace, converted into a secondary school, and the usual complement of narrow lanes, small canals and elegant foot bridges.

Scarpa appears at his door, wearing a black T-shirt which admonishes "Listen carefully". He has an impish look, emphasised by his round, bald head and ready smile. He shows me into his book-and-CD lined study, which looks out over a neighbourhood piazza, and offers me the choice of a variety of soft drinks.

Tiziano Scarpa is already known to English-reading audiences for his charming and original guidebook Venice is a Fish, published in the UK three years ago. His new book, the novel Stabat Mater, was first published in Italy in 2009 and won that year's Strega prize (the Italian equivalent of the Booker). It is set in 18th-century Venice at the Ospedale della Pietà. This ancient institution was a convent, an orphanage and a music school. The girls were trained to give concerts of sacred music of such excellence that they drew audiences from all over Europe. Famously, the Pietà employed Antonio Vivaldi as its choirmaster and composer.

The difficulty of writing about Venice, Scarpa tells me, is to avoid the postcard images that fill everyone's head and block off access to the reality of life as it has been, and is still, lived there. "When you are born in Venice, you want to get rid of anything to do with it as soon as possible," he tells me. "In fact, I went away. I went to live in Milan for 12 years." But having returned some years ago, he has found ways to write about his native city.

Although the Pietà ended its formal existence with the destruction of the Republic in 1797, one part was being used as a maternity hospital at the time of Tiziano Scarapa's birth there in 1963. When, as a child, he would walk past the place with his mother, she would remind him that he had been born there – perhaps in the very room where Vivaldi once gave instruction to the young female musicians.

Not having any sisters of his own, Scarpa used to fantasise that one or more of those children might have been "little sisters of mine". And so began an identification that ended with his having found the subject for a novel.

To research the book, he began to listen closely to the music Vivaldi wrote for female voices "as if these sisters of mine could communicate with me across three centuries. Of course, I know perfectly well that this is a fiction, but in my mind, in my soul ... I said to myself that if Vivaldi worked at the Pietà almost all his life, he knew these girls very well, with their own personality, their own character, their dreams. Maybe he poured into his music something of the personalities of these girls."

Scarpa searches for a particular track in his large collection of Vivaldi CDs and puts on "Sit nomen" from Laudate pueri Dominum. Later, he plays me the haunting and beautiful "Cum dederit" from Nisi Dominus, sung by Gemma Bertagnolli.

"If you listen to this," Scarpa says, "it's impossible not to think about the condition of the girls singing. Of course, this is a praise to the name of the Lord, but I can hear inside this prayer the expression of a condition: desperation, but also harmony and therapy. What we call elegy. You sing an elegy in front of a tomb, where you cannot be consoled."

When Scarpa used to think of his little sisters, he did so with sadness. "These girls had nothing. They had no family. They couldn't decide how to spend their time. They had no dresses of their own. They had no names, we can say, because the name that they had was a sort of bureaucratic name given to them by the institution. Some would be given the family name "Dalla Pietà" – "coming from the Pietà". There are still some Dalla Pietàs in Venice."

The desperation of Stabat Mater's protagonist, Cecilia, a 15-year-old violinist who has spent her whole life at the institution, is given expression in the letters she writes to the mother she has never known, whom she addresses, with affecting formality, as Lady Mother. Scarpa has brilliantly imagined how a sensitive child, who knows practically nothing of the world, would fill in the blanks of her experience with powerful inventions. For example, Cecilia has an imaginary friend, a Medusa figure with hair fashioned from snakes who reflects back to Cecilia her obsession with death.

Scarpa uses Cecilia's ignorance of life to let her express herself with unwonted directness. "In this era," he says, "we always put in some irony and humour when we speak about anything. Even if I am desperate, as a contemporary man or woman I always speak with a hint of irony so as not to bury you under all the weight of my problems. In this book, I wanted to cut off the ironic part of our mentality in order to dig deep inside anxiety and desperation; the black parts of the night when you think you are lost."

When Vivaldi arrives at the Pietà as the new choirmaster, he recognises Ceclia's musical ability but also understands her anguished mental state. They enter into a struggle that is characterised by her complete immersion in his music and his desire to make use of her talent for his own fame. The climax of their conflict leads to the novel's unexpected (at least by me) conclusion.

Our interview also concludes on an unexpected note. To my final question about how he finds living in Venice, Scarpa replies: "It is as if Venice were always pointing at me, telling me: 'Look at me. I am impossible but I exist. You should do something impossible too.' For artists and writers, it's an admonition."

Stabat Mater, By Tiziano Scarpa, Serpent's Tail £9.99

'Don Antonio has written a concert in which you can hear our womanly character frothing, in three phases, first gaiety, then languor, then euphoria again. This man draws feminine sounds from our bodies, he gives old men's age-plugged ears the sound version of women, our translation into sounds, as men want to hear it.'