SATB

That stands for soprano, alto, tenor, bass. That's just a scoring for choral works common enough to get an abbreviation. You may have noticed if there are choirs in your church that there are the high and lowish female sections and highish and low male sections of the choir.  SATB

Well, that's easy enough. But I also wondered, what's a baritone? Doesn't treble mean something? The three tenors don't sound that high. I never heard them singing falsetto. (That's the higher register of your voice associated with yodeling which, by the way, is really hard whether you enjoy it or not.  Try it.) If you've wondered these things, too, then read on.

When I took my music history class (instead of something useful, like the physics of oxides) we were taught that female voices are classified as soprano, mezzo-soprano (mezzo for short), and contralto where soprano is the highest.  Male voices are classified as tenor, baritone, and bass where tenor is the highest.  This was simple, and this made sense.  But then I recalled this video which I'd encountered some time prior.  In case this sounds like screeching to you, I direct your attention to Dessay's precise intonation even as she makes the leaps across the disjunct melody (wide pitch intervals between notes).  Also, notice her easy, wide, consistent vibrato (are those wide enough to be trills sometimes?), her ease singing softly and loudly, and the extra, little flourishes that she executes that just amplify the difficulty of the song.  This, in my opinion, is an excellent demonstration of virtuosity.  It's technically solid without being ostentatious.

How is this relevant?  Well, looking through the comments, I saw her described as a coloratura soprano.  Eh?  So there are different kinds of sopranos?  Well, it just so happens that beyond the six vocal ranges I just mentioned, there are also classifications into voice types.  According to the wikipedia article, sopranos can be further classified into coloratura sopranos, lyric sopranos, dramatic sopranos, soubrettes, and spintos.  The difference between these voice types depends on such things as vocal color, agility, range of the various registers, where the voice is most comfortable regardless of overall range, etc.  But it gets a little worse.  Coloratura sopranos, for instance, can be further classified as lyric or dramatic coloraturas, or as sfogato sopranos.  Compare the differences here.

This isn't just opera arcana akin to the amateur sommelier's spouting of nonsense aromas he purports to detect in a Virginian chardonnay that he thinks is French.  It's actually really important for these singers to be classified correctly.  One mezzo recently learned that she's actually a soprano, an experience that she compared to undergoing a sex change.  Had she not discovered this sooner, there would have been serious risks to her voice and career.  Maria Callas famously astounded critics early on by triumphantly filling roles written for the coloratura soprano to the dramatic soprano and even into mezzo territory, but soon wore out her voice.  You wouldn't ask a person built as a line-backer to play as a quarterback (did I get that football analogy right?) without expecting problems.  Likewise for singers.  You can work to extend your range, and certainly many singers can fill roles spanning a small range of classification.  But pushing boundaries too far can be dangerous.

But we haven't covered all of the ranges yet, have we?  Turns out treble refers to prepubescent boys or girls with a soprano range.  What about the male falsetto?  Some of you may recall the castrati popular in the Baroque era.  Through a surgical manipulation prior to puberty, the church maintained in these men child-sized vocal cords with superman-sized rib-cages to back them up.  This produced ideal qualities for "angelic" singing, but at a great cost.  Fortunately, the practice is no longer condoned.  But who's to sing the many phenomenal parts written for these poor men?  The closest modern equivalent is the counter-tenor.  I just learned this a couple days ago.  It's basically a guy who sings well in the falsetto register.  And, of course, there are subclassifications.  Some of you might find the sound disorienting, interesting, beautiful, or possibly even hot.  They don't have the huge voices and stamina of castrati, but at least they have their manhood.  And this really isn't very uncommon in popular music, is it?  Think of Prince, Matthew Bellamy, Thom Yorke, and others.

And yet, I have to wonder, by probability alone, shouldn't there be some accidental castrato sitting around in India or China that we don't know about?  Kids hurt themselves in weird ways all the time.  Wouldn't it be interesting to hear?  I'm just saying.

So there you have it.  Following the world's singers is as complicated and interesting as following baseball players.  They all have their roles, fortes, styles, career development, injuries, and so on.  It's as exciting when a seasoned singer joins a new production as when a seasoned player joins a team.  And it's as confounding to my mind trying to keep track of it all.