In situations that call for certain gestures -- a rush hour traffic dispute, for instance -- our first instinct is to extend our good old Number Three. This sometimes leads to misunderstandings:
Judge: Is it a fact that when the plaintiff asked your name, you raised your second finger?
Defendant (Loudly and confidently): Your Honor, I did not.
Pianists are particularly pentactine. When we discuss "Beethoven's Third" or "Chopin's First," we may be talking, not of concertos, but of those rather macabre hand casts the great instrumentalists had behind them. We browse for hours, studying articles in trade periodicals with names like Clavier on idiosyncrasies of this finger or that finger.
The fifth finger is that which, in the right hand, floats melodic notes at the top of the harmonic swells, while in the left, its job is to sound and shape the basic contours of the ocean floor. Vladimir Horowitz had almost freakishly independent fifths. I never figured out how extensors that flexed so far back could uncurl and hit flying hemidemisemiquavers at such speed.
Technically speaking, the fourth is the weakest and most awkward finger, being hitched to its neighbors by a pesky web of ligaments. Just point your five fingertips onto a flat surface and try to lift #4 separately. You'll appreciate what problems we have playing the inner voices of Bach.
The third finger, apart from its gesticulatory usefulness, acts as both a lever (allowing #1 to pass gracefully under it in scales and arpeggios) and a fulcrum when the whole hand and arm are rotating tremolando.
Number Two is annoyingly strong and needs equalizing if it is not to break the melodic line, or overbalance a weighted chord.
The first finger has had a somewhat vulgar reputation since Jack Horner used it to check the filling of his Christmas pie. Yahoos use it for pointing over their shoulders, or grappling beer, or rating movies on television.
But when used in a left-handed cantilena by a master technician, this finger becomes the most expressive digit of all. Listen, for example, to the brilliant Claudio Arrau's recording of the slow movement of Brahm's F minor Sonata. You'll never say "all thumbs" again.