Genus (music)
genera "type, kind") is a term used to describe certain classes of intonations of the two movable notes within a tetrachord.
According to the system of Aristoxenus and his followers—Cleonides, Bacchius, Gaudentius, Alypius, Bryennius, and Aristides Quintilianus[1]—the paradigmatic tetrachord was bounded by the fixed tones hypate and mese, which are a perfect fourth apart and do not vary from one genus to another.
Instead, they described characteristic functional progressions of intervals, which he called "roads" (ὁδοί), possessing different ascending and descending patterns while nevertheless remaining recognisable.
[5] Aristoxenus describes the diatonic genus (Ancient Greek: διατονικὸν γένος) as the oldest and most natural of the genera.
The English word diatonic is ultimately from the Ancient Greek: διατονικός, romanized: diatonikós, itself from διάτονος, diátonos, of disputed etymology.
This takes τόνος, tónos, to mean "interval of a tone"; see Liddell and Scott's Greek Lexicon Archived 2011-03-05 at the Wayback Machine and Barsky (second interpretation), below.
Aristoxenus (and Cleonides, following his example; see also Ptolemy's tunings) describes two shades of the diatonic, which he calls συντονόν (syntonón, from συντονός) and μαλακόν (malakón, from μαλακός).
[13] Syntonón and malakón can be translated as "tense" ("taut") and "relaxed" ("lax, loose"), corresponding to the tension in the strings.
Aristoxenus describes the chromatic genus (Greek: χρωματικὸν γένος or χρωματική) as a more recent development than the diatonic.
In contrast, the ancient Greek chromatic scale had seven pitches (i.e. heptatonic) to the octave (assuming alternating conjunct and disjunct tetrachords), and had incomposite minor thirds as well as semitones and whole tones.
[13] Theon of Smyrna gives an incomplete account of Thrasyllus of Mendes' formulation of the greater perfect system, from which the diatonic and enharmonic genera can be deduced.
[14] Someone has referred to this speculative reconstructions as the traditional Pythagorean tuning of the chromatic genus[citation needed]: Archytas used the simpler and more consonant 9:7, which he used in all three of his genera.
In the modern tuning system of twelve-tone equal temperament, enharmonic refers to tones that are identical, but spelled differently.
In other tuning systems, enharmonic notes, such as C♯ and D♭, may be close but not identical, differing by a comma (an interval smaller than a semitone, like a diesis).
[17] A further modern notation involves reversed flat signs for quarter-flat, so that an enharmonic tetrachord may be represented: or The double-flat symbol () is used for modern notation of the third tone in the tetrachord to follow modern convention of keeping scale notes as a letter sequence, and to remind the reader that the third tone in an enharmonic tetrachord (say F, shown above) was not tuned quite the same as the second note in a diatonic or chromatic scale (the expected E♭ instead of F).
The principal theorist of rhythmic genera was Aristides Quintilianus, who considered there to be three: equal (dactylic or anapestic), sesquialteran (paeonic), and duple (iambic and trochaic), though he also admitted that some authorities added a fourth genus, sesquitertian.
