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8 <appendix id="aharmonies" revision="$Revision: 1841 $ $Name$" userlevel="adv" |
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9 vendor="1.12" xmlns:xi="http://www.w3.org/2003/XInclude"> |
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10 <title id="atharmonies">The harmonic principle</title> |
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11 |
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12 <para>The Harmonies Attributes came from a principle known from |
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13 Antiquity and named harmonics. Harmonics are used in music as |
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14 what we known as scales. A scale contains twelve notes (when we |
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15 count the black notes on piano keys) which repeat infinitely. |
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16 Between one note and the next one with the same name, there is a |
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17 difference of pitch (the frequency of the notes) which is exactly |
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18 the double.</para> |
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19 |
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20 <para>In the Harmonies, the recipe is the same except that we only |
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21 kept ten notes and that the value is multiply by 10 at each |
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22 repetition. This scale is called the logarithmic decimal scale |
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23 and <xref linkend="tmesures"/> only gives you an approximation of |
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24 it.</para> |
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25 |
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26 <para>The important values to remember in this scale are those |
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27 associated with the value 0, 3, 5 and 10, which are 1, 2, 3 and 10 |
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28 respectively. From those ones, you can find back the full table |
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29 simply by adding and subtracting the empty spaces from the known |
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30 values, and then to replace additions with multiplications, and |
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31 subtraction with divisions. For example, to get back the value of |
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32 2, we can observe that 5-3=2, so, once the substitution done, we |
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33 have 3/2=1.5.</para> |
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34 |
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35 <para>Note that those numbers are only approximation except for 0 |
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36 (which equal exactly 1) and 10 (which equal exactly 10). A 3 |
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37 points difference is equivalent to a factor of 2.01, and a 5 |
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38 points difference is equivalent to approximately 3.2.</para> |
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39 |
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40 </appendix> |
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41 <!-- Keep this comment at the end of the file |
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