Chromatic genus

In Ancient Greek music theory, the chromatic genus (Greek: χρωματικό γένος or χρωματική) (also known as chrōma, from the Greek word χρώμα, "colour") is a genus of the tetrachord characterized by an upper interval of a minor third. The two middle notes of the tetrachord were movable (kinoumenoi) while the two outer notes were immovable (hestōtes) (Mathiesen 2001, 6.iii.c). The movable members of the tetrachord (the pyknon) is divided into two adjacent semitones (hence this genus is the origin of the modern term, chromatic).^{[citation needed]}

Note that the scale generated by the chromatic genus is not like the modern chromatic scale. The modern (18th century) well-tempered chromatic scale has 12 pitches to the octave, and consists of semitones of various sizes; the equal temperament common today, on the other hand, also has 12 pitches to the octave, but the semitones are all of the same size. In contrast, the ancient Greek chromatic scale had seven tones to the octave (assuming alternating conjunct and disjunct tetrachords), and had undivided minor thirds as well as semitones.

The (Dorian) scale generated from the chromatic genus is composed of two chromatic tetrachords:

Chromatic genus of the Dorian octave species

Whereas in modern music theory, a chromatic scale is:

D D♯ E F F♯ G G♯ A A♯ B C C♯ D D♯ E ...

Tunings of the chromatic

Thrasyllus of Mendes gave the traditional Pythagorean tuning of the chromatic genus:

hypate   parhypate      lichanos                             mese
 4/3       81/64         32/27                               1/1
  | 256/243  |  2187/2048  |              32/27               |
-498       -408          -294                                 0 cents
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Archytas replaced the 81/64 with the simpler and more consonant 9/7, which he used in all three of his genera:

hypate parhypate        lichanos                             mese
 4/3     9/7             32/27                               1/1
  | 28/27 |    243/224     |              32/27               |
-498    -435             -294                                 0 cents

Didymus's chromatic has only 5-limit intervals, with the smallest possible numerators and denominators. Also note that the successive intervals are all superparticular numbers:

hypate     parhypate lichanos                                mese
 4/3          5/4      6/5                                   1/1
  |   16/15    | 25/24  |                 6/5                 |
-498         -386     -316                                    0 cents

Byzantine Music

In Byzantine music the chromatic genus is the genus on which the 2nd mode and 2nd plagal mode are based. The "extra" mode nenano is also based on this genus.

See also

• Diatonic genus
• Enharmonic genus
• Diatonic and chromatic

Sources

• Mathiesen, Thomas J. 2001. "Greece, §I: Ancient". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.