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Music

Scales and harmoniai

Tetrachords, genera, keys and octave species: the structure of ancient Greek scales.

Scales · 1 of 5

Tetrachords and the three genera

Greek scales were not built from the octave down, but from the fourth up. The fourth, the fifth and the octave were the concords (symphōna). Every other interval was a discord, acceptable in a melody but not as a frame.[1]

The unit of construction is the tetrachord. A tetrachord is four notes spanning a fourth. Scales are strings of tetrachords. Two tetrachords that share a note are called conjunct. Two that are separated by a whole tone are called disjunct.[2]

Tetrachord: Four notes bounding a perfect fourth. Its two outer notes are fixed. The two inner ones move, and where they stand decides the genus.

Fixed and moving notes

The two outer notes of a tetrachord are the standing notes, and they never change. The two inner notes are the moving notes. They can be set in three ways, and the three settings are called the genera:[3]

  • In the diatonic the fourth is filled by a semitone and two tones: e f g a.
  • In the chromatic the two inner notes lie a semitone apart, leaving a minor third above: e f f♯ a.
  • In the enharmonic they lie about a quarter-tone apart, leaving a ditone above: e e↑ f a.[4]

A ditone is an interval of two whole tones. In the chromatic and enharmonic the two moving notes crowd together at the bottom. The three close-packed notes are then called the pyknon.[3] These words mean something quite different from their modern uses.[5]

a tetrachord e–a, drawn to scale (500 cents) diatonic efga ½11 chromatic eff♯a ½½1½ enharmonic ee↑fa ¼¼2 filled: standing notes · ring: moving notes · shaded: the pyknon
efgadiatoniceff♯achromaticee↑faenharmonic
The tetrachord e–a in the three genera, as in the diagram above. The enharmonic e↑ is a quarter-tone above e. The Music theory page lets you drag the moving notes yourself.

Where the genera came from

The modern ear takes the diatonic for granted. But in the classical period the non-diatonic genera predominated. An octave might contain a single whole-tone step: the disjunction between its two tetrachords.[6]

Aristoxenus believed that the enharmonic had grown out of an older three-note form, e f a, by dividing its semitone. His evidence was that the libation-tune of Olympus, played in the old style, left the semitone undivided.[7] West turns this round. For him the enharmonic and the diatonic are alternative developments of the same pentatonic matrix, in which a fourth was filled by one note only. The chromatic grew the same way, from a division of the tone and the minor third.[7]

Hagel finds the physical source in the aulos. Pipes with evenly spaced holes gave steps of a tone and of a three-quarter-tone. Half-stopping a hole produced the enharmonic microtone.[8]

In the fifth century serious music, Pindar’s and the tragedians’ included, was normally enharmonic. The chromatic, a “colouring”, came in with the professional citharodes from about the middle of the century, and it was said to make men soft. The New Music of Timotheus and Philoxenus modulated among all three genera.[9]

The true quarter-tone was in use in the early fourth century. Aristoxenus defended the enharmonic, with its ditone. But before long the genus was dead in music of the highest level.[10]

By the Roman period the scores are almost wholly diatonic. The diatonic, Aristides Quintilianus explains, is natural. The chromatic is for the trained. The enharmonic is for exceptional musicians, and impossible for most.[11] The notation never distinguished the chromatic from the enharmonic. Nowacki takes this as a sign that the enharmonic was already obsolescent when the system took its final form.[12]

Faded wall painting: a seated bearded satyr teaches a youth standing before him.
Marsyas teaching Olympus, Herculaneum

Shades

The diagram draws the inner notes at round values, but the theorists allowed them a range. Aristoxenus gives each genus bands within which the moving notes may lie. He names six “shades”:

  • the enharmonic (¼, ¼, 2);
  • three chromatics: soft, hemiolic and tonic, the last ½, ½, 1½;
  • two diatonics: soft (½, ¾, 1¼) and tense (½, 1, 1).[13]

The Pythagoreans gave ratios instead. They were Philolaus, Archytas, Eratosthenes, Didymus and finally Ptolemy, who lists seven divisions, one of them his own invention.[14]

Notes

  1. ^ West 1992, pp. 160–161.
  2. ^ West 1992, p. 161.
  3. ^ a b West 1992, p. 162.
  4. ^ West 1992, p. 162; Anderson 1994, p. 198.
  5. ^ West 1992, p. 162 n. 1.
  6. ^ West 1992, pp. 161–162.
  7. ^ a b West 1992, pp. 163–164.
  8. ^ Hagel 2009, p. 443.
  9. ^ West 1992, pp. 164–165.
  10. ^ Hagel 2009, pp. 446–447.
  11. ^ West 1992, pp. 165–166.
  12. ^ Nowacki 2020, pp. 46–47.
  13. ^ West 1992, pp. 168–169.
  14. ^ West 1992, pp. 167–171; see the Aristoxenus and the Pythagoreans tab.
Picture credits on this page
  1. Behind the title: Muse tuning two kitharai: interior of an Attic white-ground cup by the Hesiod Painter, c. 470–460 BC, from Eretria. Paris, Louvre CA 482. Hesiod Painter; photo: Jastrow · Public domain · via Wikimedia Commons
  2. The musical education of Olympus by Marsyas: fresco from the Augusteum at Herculaneum. Naples, Museo Archeologico Nazionale. Yair Haklai · CC BY-SA 4.0 · via Wikimedia Commons
  3. Replica of a chelys, the tortoise-shell lyre, built by Kostas Kotsanas: Museum of Ancient Greek Technology (shown at Heraklion, Crete, July 2022). Eunostos · CC BY-SA 4.0 · via Wikimedia Commons
  4. Plato: Roman copy of the portrait made by Silanion c. 370 BC for the Academy in Athens. Rome, Musei Capitolini MC 1377. Marie-Lan Nguyen · CC BY 2.5 · via Wikimedia Commons · background removed
  5. Aristoxenus, Elements of Harmony: Vatican, Biblioteca Apostolica Vaticana, Vat. gr. 191, fol. 299r (1296). Biblioteca Apostolica Vaticana manuscript (reproduction) · Public domain · via Wikimedia Commons
  6. Woodcut showing Pythagoras with bells, glasses, a monochord and pipes in Pythagorean tuning. From Theorica musicae by Franchino Gaffurio, 1492. Franchino Gaffurio (publisher); woodcut by an unknown artist · Public domain · via Wikimedia Commons