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Two of our fragments preserve music from the end of the fifth century BC, in both cases from choruses of Euripides. In a few other instances the music cannot be later than the third century BC and might be earlier. But the bulk of our material is either late Hellenistic or from the Roman period. It tells us a certain amount about the music of those times, but not much about that of the Classical age. |
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A catalogue of the surviving musical documents, with transcriptions of the better-preserved items, will be found in Chapter 10. Citations of them elsewhere are accompanied by a bold-face numeral referring to the catalogue. |
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Here is an excerpt from a piano keyboard. It covers an octave, from one C to the next. The adjacent octaves would look exactly the same: the octave is a repeating structure. |
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Why does the octave enjoy this status? Why are two notes an octave apart both called C, as if they were the same? It is because notes separated by this interval blend supremely well together, so that when they are sounded simultaneously one is hardly aware that they are not the same. Because of their affinity, a scale begun on one of them achieves a sense of completeness when it reaches the other. Many melodies take an octave for their compass for the sake of this sense of wholeness. |
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There is a physical reason for the consonance of notes at the octave. They travel on sound-waves whose vibration-frequencies stand in the simple ratio 2: 1, the rapider one corresponding to the higher note.12 This means that there is a constant coincidence of wave-peaks, every peak of the slower wave matching every second peak of the faster one. The more regularly such agreement occurs, the better the blend perceived between two sounds. |
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Taking the white and black notes of the keyboard without distinction, we see that they divide the octave into twelve equal steps of a |
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12 The same ratio will apply to the lengths of vibrating strings. provided that they are of the same material, thickness, and tension: a string that is just half the length of anotheror a single string stopped at its mid-pointwill give out a note an octave higher. |
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