This practice was begun in the 16th century and reached its peak in 17th and 18th century opera. The male heroic lead would often be written for a castrato singer (in the operas of Handel for example). When such operas are performed nowadays, a woman or countertenor takes these roles.
Castration before puberty (or in its early stages) prevents the boy's larynx from being fully transformed by the normal physiological effects of puberty. As a result, the vocal range of prepubescence (shared by boys and girls) is largely retained, and the voice develops into adulthood in a unique way. As the castrato's body grows (especially in lung capacity and muscular strength), and as his musical training and maturity increase, his voice develops a range, power and flexibility quite different from the singing voice of the adult female, but also markedly different from the higher vocal ranges of the uncastrated adult male (see soprano, mezzo-soprano, alto, sopranista and contralto).
Probably the most famous castrato was the 18th century singer Carlo Broschi, known as Farinelli. In 1994 a film was made about him, Farinelli Il Castrato.
In 1870 the practice of castrating promising young singers was outlawed in Italy, the last country where it was still in custom.
The only acknowledged castrato to make phonograph recordings was Alessandro Moreschi, the last surviving castrato of the Pope's choir. Moreschi recorded disc recordings for the Gramophone & Typewriter Company in 1902 and again in 1904. Critical opinion is divided about Moreschi's recordings; some say they are of little interest other than the novelty of preserving the voice of a castrato for Moreschi was a mediocre singer, while other critics detect the remains of a quite talented singer who was unfortunately past his prime by the time he recorded.
In more modern times, Ugo Farell has been suspected of being a castrato.
There have also been reported cases of so-called "natural castrati" who were born with hormonal disorders that reproduce the above "desired" effects of castration without the surgeon's knife.
Some uncastrated male singers are able to use their voices up into the soprano register, apparently without the use of the falsetto voice, and are known as sopranistas. There are very few such singers performing today. Sopranistas are also able to perform some music which was written for castrati, and composers such as Rossini wrote parts specifically for sopranista.
See also: eunuch