In historical dramas and dramas pretending to be historical, the eunuch’s pronunciation is always high-pitched, but lacks the resonance of the oral and chest cavities, as well as unnatural breathiness, so their voices sound strange. Although the voice of a real eunuch is not like this, this is how it is portrayed in dramas, after all, there are indeed differences in the physical functions of eunuchs.
The eunuch’s castration surgery is now called orchiectomy. The testicles produce testosterone, which brings about the development of male secondary sexual characteristics. Therefore, if it is removed before puberty, changes in male secondary sexual characteristics, such as thickening of the vocal cords, will stop, and the voice will remain at the pitch of children, early adolescents, or adult women. The following are specific cases:
Castrato appeared in Italy in the mid-16th century. The specific details of their birth are unknown, but some people did perform orchiectomy on boys around 8-10 years old, and then trained them to become opera musicians who could produce high-pitched female-like sounds.
The last castrato singer was approximately Alessandro Moreschi, a little over 100 years ago. Fortunately, recording technology was already available, so now you can hear his voice, which sounds like a mezzo-soprano.
However, recording equipment at that time was expensive, and only singers with high commercial value and some people with noble status could use it, so the lowly eunuchs did not leave any recordings. However, the eunuch Sun Yaoting lived until 1996 and was interviewed before that, so you can hear his voice.
Sun Yaoting’s voice in his old age was like that of an ordinary old woman, so his voice when he was young was probably as ordinary as a woman’s.
P.S.: After the testicles are removed, the body usually still produces a small amount of testosterone, which results in castratos and eunuchs having a lower probability of having soprano voices. Now that we know the principle, we can rely on anti-androgens and use chemical castration to more safely achieve voice adjustment. Even if testosterone adjustment is not performed before puberty, surgery can be performed on the vocal cords later, but that is another story.