tetrachord

/te-truh-kawrd/US // ˈtɛ trəˌkɔrd //UK // (ˈtɛtrəˌkɔːd) //

四弦琴,四音符,四音琴,四音图

Definitions

n.名词 noun

1
Music.
- : a diatonic series of four tones, the first and last separated by a perfect fourth.

Within each tetrachord the intervals depend upon the Genus (genos).
That is to say, the tetrachord b c d e is not written , but : and d e♭ f g is not , but .
In ancient language, the tetrachord Synmmenn (a-b♭-c-d) takes the place of the tetrachord Diezeugmenn.
In practice it appears that musicians tuned the tetrachord b-e of this scale with the Pythagorean two Major tones and leimma.
In this case, as the pyknon forms the lower part of a tetrachord, there are two possibilities.