Of possible interest (or everyone may already know)
I once fell down a research rabbit hole about how 18th cent castrati might have achieved some famous vocal special effects.

I just encountered the Righteous Brothers live performance of Unchained Melody https://www.youtube.com/watch?v=m0EBs6uRgtw
I watched a video where someone ran the audio through some test gear, and other videos where voice coaches commented on how he was doing what he was doing.
I had a lot of deja vu.
He hit notes from D3 to G5.
#BaroqueSun

Righteous Brothers -- Unchained Melody (Live, 1965) (Picture and Sound Restored)

YouTube

@ElyseMGrasso I was going to comment that there was a film about Farinelli "a few years ago" - but as it turns out the "a few years ago" in question was back in 1994... 🙈

Anyway, I seem to remember that to recreate Farinelli's voice, the producers mixed recordings of a (female) soprano singer and a (male) countertenor.

@ElyseMGrasso I should look up "unchained" for euphem... nuthin! #BaroqueSun