Tetrachordal thinking

[Neil Haverstick:]

> Here's a question which I was originally going to post
> privately to Chalmers, but thought I'd air it out here for
> maximum response; why are scales formed by tetrachords in the
> first place? I've read about them for many years, and all of a
> sudden I realized that I don't know the fundamental reason behind
> their origin. Any thoughts are surely appreciated....thanks...
> Hstick

There are two main reasons that scholars have accepted for the
emergence of music theory in a system of tetrachords:

1) Tetrachords provide the smallest _diatonic_ interval-structure
that repeats. In other words, in a diatonic scale, that is,
one with steps of the sizes "tone" and "semitone", the interval
structure of the four notes within a "perfect 4th" will contain
one "semitone" and the rest are "whole tones". This is the
smallest diatonic unit that provides a "semitone", and thus the
unique smaller step which identifies the structure. In genera
other than the diatonic, the tetrachord still encompassed the
main identifying interval, be it a 6/5 in the chromatic, a
5/4 in the enharmonic, or some other ratio of a "3rd".

2) Ancient Greek was a tonal language, where the _pitch_ of a
vowel affected its meaning (like modern Chinese). It is
assumed that during poetic speech, the "melody" of the phrase
covered approximately the range of a "4th", thus this became
the important unit to the Greeks.

Joseph L. Monzo
monz@juno.com
4940 Rubicam St., Philadelphia, PA 19144-1809, USA
phone 215 849 6723

_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]