Image by Real Distan
Recently I saw a wonderful ballet which featured a segment titled "Castrato". In 18th-century Europe, young boys who had a great singing voice would be castrated to assure that they do not loose their voices once they go through puberty.
The arias played made me look up more about the castrato and I learned that the most famous of them was a male opera singer named Carlo Broschi, known as Farinelli (1705 - 1782). You can read all about this very talented singer and his career here.
"Castrati were particularly known for their unique timbre: because of the surgery performed on them, their voice did not change with puberty. Upon adulthood, the size of their thoracic cage, their lung capacity, their physical stamina and their strength were usually above that of most men. They had, as a consequence, great vocal power, and some were able to sing notes for a minute or more. Finally, a small and flexible larynx, and relatively short vocal chords allowed them to vocalize over a rather wide range (over 3 and 1/2 octaves) and to sing with great agility (they could control wide intervals, long cascades and trills)." Source:
The Singer Farinelli and Friends by Jacopo Amigoni