The practice of castrating young boys to preserve their voices became institutionalised in the Sistine Chapel of Renaissance Rome as a response to the enforcement of St Paul's edict against women singing in church, and it continued until 1870, when the power of the papacy was finally curtailed. The creation of castrati was never officially condoned by the Church, but it was nevertheless happy to employ singers who had met with unfortunate "accidents" as children.
At their peak, between 1650 and 1790, castrati were the operatic superstars of their day, and played an essential role in the development of the artform. If today we have the Three Tenors, then the public loved the Three Castrati, and 1780s London was on fire with the money-spinning joint concerts of Rubinelli, Pachierotti and Marchesi.
The last celebrity castrato, Alessandro Moreschi, died almost unnoticed in 1922, a relic from an age that prized contrivance above all else. His voice, recorded on wax cylinder in 1904 (and released on CD by Pearl), is the only known recording of a castrato. Those bewitching appoggiaturias still retain some of their eerie brilliance, the voice sounding something like a boy's but with three times the power and a lifetime's emotional experience behind it. It makes the skin creep, yet is extraordinarily beautiful. These days women tend to take castrato roles like that of Julius Caesar in Handel's opera, but the original sound of one of the top-ranking castrati can only be guessed at.
Farinelli contains a scene where its star hits and sustains, with pulsing intensity, the very highest notes in his register, while women in the audience faint and afterwards proclaim that they have experienced a musical orgasm. Famous castrati were often mobbed by adoring fans, who would shout "Eviva il coltello!" (Long live the knife). Many women found them sexually intoxicating and a case could be made that castrati were the first pop idols. Michael Jackson is the perfect contemporary castrato: a childhood prodigy, his strangely unbroken voice the source of his legendary wealth, a child-adult drifting between ages and sexes, a "freak" who excites public adoration and disgust in equal measure.
This feeling of alienation and sexual ambiguity has fascinated two gay composers; Gerald Barry and Nick Bloomfield. Many castrati had affairs with women; some even married. But for Bloomfield, castrati are a "metaphor" for the sexual outsider. Irish composer Barry, too, is fascinated by the gender ambiguities of the castrato voice. His opera The Intelligence Park, loosely based on the life of a rakish castrato named Tenducci, was staged at the Almeida in the late 1980s. Nick Bloomfield's 1990 collaboration with Neil Bartlett, Sarrasine, was based on a Balzac story about a French sculptor falling in love with a castrato in the conviction that he is a woman. Casanova himself fell in love with a castrato, only to find that "he" was a "she". This raises the question of how many faux castrati there were floating around in an age when fine women singers were forced into travesty in order to earn the vast fees available to castrati.
Anne Rice (of Interview with the Vampire) was also attracted to the subject's rich themes of tragedy and perverse eroticism in her novel Cry to Heaven, which is also based on the Farinelli story. And even Kingsley Amis had a stab at it in his long-forgotten novel The Alteration, published in 1976, a "what if" storyline built around a modern catholic Euro-state that wants to revive the practice on a budding chorister.
Historically, the younger the boy when put to the knife, the higher and better the voice. Hence most boys were castrated between seven and 10. Charles Burney travelled round Italy in the 1770s in search of the centre of this lucrative but semi-legal trade and found that there were shops in Naples that provided barber-surgeons to carry out the operation (more of a snip than a serious mutilation, according to Charles d'Ancillon's Traite des Eunuques of 1707).
In the 18th century it is estimated that 4,000 boys a year were subjected to castration, mostly from poor families hoping to strike paydirt. Most were castrated on spec and never had the talent to take them to the top. We read about the famous castrati, but never about the tens of thousands of neutered males who remained simply castrated ploughmen or olive-pickers.
After the operation, musically talented young castrati were force-fed music like foie-gras geese. Their technique was exceptional as a result. At the age of 18, they would be expected to make their debuts and thereafter, as successful opera soloists, could expect to make at least pounds 5,000 a year during the 18th century - about a baronet's income with a large estate in Hampshire. Castrati were feted by royalty and Farinelli's influence in the Spanish court has been likened to that of Rasputin in imperial Russia.
Martin Neary, choirmaster at Westminster Abbey, is sceptical about the quality of the castrato voice. While the boy's voice may have been preserved after a fashion, he suspects that "it could never have approached the golden period in the year just before a boy's voice breaks... I believe they had the power but not the great heights, and with modern training a boy's voice is a much better instrument than it was in the time of the castrati."
So, should Aled Jones have been castrated? Some, looking at the spotty teenager who once said he wanted to be like Terry Wogan, would say yes. And no doubt Macauley Culkin's parents are counting the cost of those hormones: an artificially extended childhood (as was visited upon the child star of TV sitcom Different Strokes) would be worth millions. The pressures to produce castrati have not entirely gone away and they have, after all, been singing in living memory.
Nick Bloomfield recounts rumours of the continued existence of castrati in Catholic South America, a possibility that makes the eyes of some early music fanatics light up with guilty interest. They can but imagine that vanished and chillingly intense voice which once ravished susceptible listeners into delirium. And, following Kingsley Amis's vision, they might envisage the little star chorister of The Choir, his voice entombed by a surgeon's knife, singing plaintive notturni to the aged and reclusive Queen Diana in Kensington Palace 40 years from now.
n Ross King's 'Domino', published by Sinclair-Stevenson pounds 10. Julian Rathbone's 'Intimacy' published by Victor Gollancz pounds 15.99. 'Farinelli: il Castrato', the movie, directed by Christophe Rousset, released by Guilt on 3 November; soundtrack released by Auvidis Travelling K1005