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cles and his school. Eratocles enumerated the seven species of the octave in one genus, which must have been the enharmonic, and showed that they arose by cyclical transfer of intervals from one end to the other. But (according to Aristoxenus) he had no awareness of the rules controlling the sequence of intervals and the forms of tetra-chords and pentachords. He observed only that from the tetrachord the melodic scale divides in two in both directions, in other words, the next tetrachord may be conjunct or disjunct. He failed to say why, or whether it is true for all tetrachords.24 Eratocles' date is uncertain, but the notion of the scale 'dividing in two' seems to be reflected in Ion of Chios' epigram on the eleven-stringed lyre, not later than 422 BC, where he speaks of the instrument's 'ten-step arrangement and (?) concordant road-junction(s) of harmonia'. The point is perhaps that this lyre could modulate between the synemmenai and diezeugmenai tetrachords.25 |
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The purpose of enumerating the octave species was to show how modally different scales were generated from a single source. Eratocles must have interpreted existing harmoniai as approximations to octave species, disregarding other individual features that they might have. He was presumably responsible for the labelling of the species with modal names:26 |
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If we compare the Damonian scales set out on p. 174, we see that the four whose names match those in the above table require only a little adjustment to make them fit the homonymous species-pattern, so far as their scheme of intervals goes, except that the Damonian Lydian corresponds to Eratocles' Hypolydian. Transposed to the pitches used above, they appear as |
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24Harm. 1. 5-6, cf. 1. 2, 2. 35, 36. |
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25 Ft. 32 West. For the road-junction image cf. Aristox. Harm. 3.66f., Arisrid. Quint. pp. 116.18-117. 17. |
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26, See p. 186. The sources are post-Aristoxenian, but their language implies that the system and nomenclature were pre-Aristoxenian; see Winnington-Ingram, Mode, 52. I give the table in its original enharmonic form. The diatonic version came later. |
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