1. All children are considered trebles, with the same approximate range as a soprano. It isn’t until puberty that both girls and boys experience a lengthening and thickening of vocal folds that change their vocal range, with males’ folds becoming considerably longer and thicker than females’.
   
2. Well, usually, anyway. Castrati were male singers castrated before puberty. Without the normal adult male testosterone levels, they remained natural trebles.
   
3. Castrati were often highly paid, and in less enlightened times, some parents castrated their sons in hopes of cashing in.
   
4. The only surviving recordings of a castrato performing solo are from 1904 by Alessandro Moreschi. He hits notes common to a soprano with no apparent strain.

1. An entirely different sort of vocal manipulation, yodeling, is a fast alternation between low notes and falsetto.
   
2. Whether throat singing, yodeling or just plain speaking, there are more baritones among males than either basses or tenors. Similarly, the middle range — mezzo-soprano — is the most common of female vocals.

• Tuva, as one might expect, is where Tuvan throat singing, or Khöömei, originated. The nomadic people of this small corner of Siberia prize multiple pitches in their music rather than single, clear tones.
• Some throat singers can produce four tones simultaneously.
  
• To understand throat singing technique, imagine bagpipes. Just as pipers first produce a low drone and then layer on additional tones, throat singers start with a droned vocalization and then manipulate their vocal folds, root of the tongue or epiglottis — a flap of cartilage at the base of the tongue — to add additional notes.

Conversational voice is about 60 decibels, but the loudest human voice, according to Guinness World Records, belongs to teaching assistant Jill Drake of Kent, England. Her scream of 129 dBA was equivalent to noise levels at an AC/DC concert, and about 30 dB louder than a jackhammer.

1. Researchers at the National Center for Voice and Speech theorize that singing is a more right-hemisphere brain function, while speaking is more left-hemisphere dominant. This dichotomy is why some victims of stroke, unable to speak, can still sing.
2. 
   It’s also why some famous singers — including Carly Simon, Mel Tillis and Bill Withers — ply their trade with no problem, but sometimes stutter in conversation.

For decades, scientists thought a key element of generating voice was the Bernoulli effect, the same change in relative air pressure that allows airplanes to fly and curveballs to befuddle batters.

We now know, however, that voice generation is far more complex. Muscles in the vocal folds provide resistance to air in the lungs. As air is exhaled, it pushes between the folds, which open and close rapidly. Air above the folds is alternately compressed and decompressed, creating sound waves.