Page "Castrato" Paragraph 2
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As the castrato's body grew, his lack of testosterone meant that his epiphyses ( bone-joints ) did not harden in the normal manner.
Operating through small, child-sized vocal cords, their voices were also extraordinarily flexible, and quite different from the equivalent adult female voice.
Their vocal range was higher than that of the uncastrated adult male ( see soprano, mezzo-soprano, alto, sopranist, countertenor and contralto ).
Listening to the only surviving recordings of a castrato ( see below ), one can hear that the lower part of the voice sounds like a " super-high " tenor, with a more falsetto-like upper register above that.
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