“Soprano * Alto * Tenor * Bass
The four voices required by a chorus are (descending in pitch) soprano, alto, tenor, and bass. The voices have their instrumental counterparts in the string quartet–one of the abiding images of Western high culture, as if a group of four musicians can aspire to express something beyond our humanity. It was Mozart (who wrote twenty-one string quartets) who perfected the form, using violin, two violas, and a cello, though some argue that with the addition of a third viola and the composition of his six string quintets he perfected the form.”
Excerpted from: Rogerson, Barnaby. Rogerson’s Book of Numbers: The Culture of Numbers–from 1,001 Nights to the Seven Wonders of the World. New York: Picador, 2013.