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6 >
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7
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8 <head>
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9 <title>Temperament Ontology: Temperament Ontology</title>
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14 </head>
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15
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16 <body>
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17
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18 <h1 id="title">The Temperament Ontology</h1>
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19
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20 <!--<h2 id="subtitle">LONG Temperament </h2>-->
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21
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22 <h3 id="mymw-doctype">Working Draft — 18 Dec 2009</h3>
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23
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24 <dl>
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25
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26 <dt>This version:</dt>
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27 <dd><a href="http://purl.org/ontology/temperament/draft1-20091218/">http://purl.org/ontology/temperament/draft1-20091218/</a></dd>
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28
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29 <dt>Latest version:</dt>
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30 <dd><a href="http://purl.org/ontology/temperament/">http://purl.org/ontology/temperament/</a></dd>
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31
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32 <dt>Last Update: 18. Dec. 2009.</dt>
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33 <dd>Date: 18. Dec. 2009.</dd>
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34
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35 <dt>Editors:</dt>
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36 <dd>Gyorgy Fazekas, Centre for Digital Music Queen Mary University of London</dd>
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37
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38 <dt>Authors:</dt>
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39 <dd>Gyorgy Fazekas, Dan Tidhar, Centre for Digital Music Queen Mary University of London</dd>
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40
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41 <dt>Contributors:</dt>
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42 <dd>See <a href="#acknowledgements">acknowledgements</a></dd>
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43
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44 </dl>
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45
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46 <p class="copyright">You are granted a license to use, reproduce and create derivative works of this document under <a rel="license" href="http://creativecommons.org/licenses/by/3.0/">Creative Commons</a>.</p>
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47
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48 <!-- ===================================================================== -->
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49
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50 <hr />
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51
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52 <h2 id="abstract">Abstract</h2>
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53 <p>
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54 The temperament ontology can be used to give a detailed description of the tuning of an instrument.
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55 It is developed in the OMRAS2 project, and intended to be used in conjunction
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56 with the <em><a href="http://purl.org/ontology/mo/">Music Ontology</a></em>,
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57 for example, when describing the tuning that was used in a particular harpsichord recording.
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58 </p>
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59
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60 <h2 id="status">Status of this Document</h2>
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61 <p>
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62 <strong>This is a work in progress!</strong> This document is changing
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63 on a daily if not hourly basis. Comments are very welcome, please send
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64 them to <a href="mailto:gyorgy.fazekas@elec.qmul.ac.uk">gyorgy.fazekas@elec.qmul.ac.uk</a>. Thank you.
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65 </p>
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66
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67 <h2 id="contents">Table of Contents</h2>
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68 <ol id="toc">
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69 <li><a href="#intro">Introduction</a>
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70 <ol>
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71 <li><a href="#s11">About instrument tuning</a></li>
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72 <li><a href="#s12">An open-ended temperament description model</a></li>
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73 <li>
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74 <a href="#s13">The many ways of describing temperaments</a>
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75 <ol>
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76 <li><a href="#s131">The Circle of Fifths</a></li>
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77 <li><a href="#s132">Deviation from Equal Temperament</a></li>
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78 </ol>
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79 </li>
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80 </ol>
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81 </li>
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82 <li><a href="#sec-glance">Temperament ontology at a glance</a></li>
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83 <li>
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84 <a href="#overview">Temperament ontology overview</a>
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85 <ol>
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86 <li><a href="#s31">Example</a></li>
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87 </ol>
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88 </li>
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89 <li><a href="#reference">Cross-reference for Temperament classes and properties</a></li>
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90 </ol>
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91
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92 <h3>Appendixes</h3>
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93 <ol id="appendix">
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94 <li><a href="#references">Normative References</a></li>
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95 <li><a href="#changes">Changes in this version</a> (Non-Normative)</li>
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96 <li><a href="#acknowledgements">Acknowledgements</a> (Non-Normative)</li>
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97 </ol>
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98
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99 <hr />
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100
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101 <!-- ===================================================================== -->
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102
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103 <h2 id="intro">1 Introduction</h2>
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104
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105 <p>The temperament ontology aims to describe instrument tuning systems and their particularities.
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106 It may also be used to characterise a (potentially unknown) temperament that was used when tuning an
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107 instrument for a particular performance or recording. <br><br>
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108 At this stage the ontology is far from exhaustive. We primarily deal with
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109 temperaments in western tonal music with an emphasis on tuning keyboard instruments.
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110 One important objective is to be able to describe arbitrary temperaments,
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111 or express the results of automatic temperament extraction from audio recordings.
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112 </p>
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113
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114 <h3 id="s11">1.1 About instrument tuning</h3>
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115
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116 <p>Tuning an instrument consists of choosing the frequency values and spacing (or ratio) of pitches that are used.
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117 Pure (just) intervals of pitches correspond to whole number ratios of their frequencies, however
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118 these ratios are not compatible with each other as they arranged in scales (the way octaves are divided into discrete pitch classes) in western music.
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119 For example, it is not possible to fit twelve pure fifths (3:2)^12 into seven octaves (2:1)^7. The difference
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120 is called the Pythagorean or Ditonic comma (23.5 cents). This difference has to be
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121 tempered out ---that is, some (or all) fifths has to be mistuned slightly in order to
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122 fit them. There are many tuning systems. Most commonly, they differ in the way they compromise
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123 pure intervals to solve this problem. </p>
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124
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125
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126 <h3 id="s12">1.2 An open-ended temperament description model</h3>
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127 <p>There is no mutual agreement in the literature on the description or classification
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128 of temperaments. Therefore, in this ontology we do not impose a
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129 hierarchy between types of temperaments. We define an opaque
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130 top-level temperament concept. Subclasses of this concept can be used
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131 in describing individual temperaments, if necessary, using multiple class memberships.
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132 Since there is more than one way to associate tuning systems with their properties,
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133 we treat temperament descriptions as concepts as well,
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134 and use reification to keep the model open and extensible.</p>
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135
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136 <p><center><img src="TemperamentDescription.png" alt="Using the Circle of Fifths to describe a temperament." width="850">
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137 <br><br>Figure 1. Overview of the temperament ontology.</center></p>
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138
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139
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140 <h3 id="s13">1.3 The many ways of describing temperaments</h3>
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141
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142 <p>Temperaments can be characterised in lots of different ways.
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143 The most common methods are using either the circle of fifths or
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144 give the pitch deviations from equal temperament. We define these
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145 descriptions as concepts in the ontology, however, other descriptions
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146 may be used and defined in the future.
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147 (For example, one might find it convenient to express the same information using the circle of fourths.)</p>
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148
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149 <h4 id="s131">1.3.1 The Circle of Fifths</h4>
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150 The circle of fifths has several uses in music theory.
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151 It shows the harmonic relationships of the twelve major and minor keys.
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152 It can also be seen as a circle of the corresponding pitch class intervals,
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153 such as (C-G), (G-D), (D-A) etc... If we go around the circle using pure fifth
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154 intervals, it wouldn't close. What remains is the Pythagorean comma.
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155 Hence, it is often used to describe temperaments by showing how
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156 the comma is distributed among the intervals to close the circle.
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157 (Note that there are several types of commas related to different
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158 tuning problems. These are defined in the ontology.)
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159
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160 <!--<p><center><img src="CircleOfFifths.png" alt="Using the Circle of Fifths to describe a temperament." width="350"></center></p>-->
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161
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162 <p>...</p>
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163
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164 <h4 id="s132">1.3.2 Deviations from Equal Temperament</h4>
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165
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166 <p>In equal temperament an octave is divided into twelve equal intervals.
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167 As a result only octaves are pure. All other intervals are impure, and the
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168 deviation from pure is different in case of each interval. Since equal temperament
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169 has become very common, other temperaments are often described by
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170 the frequency deviations (in cents) of each pitch class from the
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171 corresponding pitch class in equal temperament.</p>
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172
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173 <!-- ===================================================================== -->
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174
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175 <h2 id="sec-glance">2. Temperament ontology at a glance</h2>
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176
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177 <p>
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178 An alphabetical index of Temperament terms, by class (concepts) and by property
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179 (relationships, attributes), are given below. All the terms are hyperlinked
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180 to their detailed description for quick reference.
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181 </p>
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182
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183 <!-- The list of classes and properties goes here -->
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184 %s
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185 <!-- End of the terms list -->
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186
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187 <p>...</p>
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188
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189 <!-- ===================================================================== -->
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190
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191 <h2 id="overview">3. Temperament ontology overview</h2>
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192
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193 <!--<p>The Temperament definitions presented here are ...</p>-->
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194
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195 <h3 id="s31">3.1. Example</h3>
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196
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197 <p>Here is a very basic example describing a pitch class interval in the Valotti temperament using the circle of fifths.</p>
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198
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199 <div class="example" style="white-space: pre-wrap;">
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200 <pre>
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201 @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
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202 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
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203 @prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
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204 @prefix tm: <http://purl.org/ontology/temperament/> .
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205 @prefix pc: <http://purl.org/ontology/temperament/pitchclass/> .
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206
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207 :ValottiTemperament a tm:WellTemperament;
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208 tm:description :ValottiDescription1 .
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209
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210 :ValottiDescription1 a tm:CircleOfFifths;
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211 tm:interval [
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212 a tm:FifthInterval ;
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213 tm:deviation [
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214 a tm:IntervalDeviation ;
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215 tm:comma tm:PythagoreanComma ;
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216 tm:value "-0.16667"^^xsd:float ;
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217 rdfs:label "-1/6"
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218 ] ;
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219 tm:lower pc:C ;
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220 tm:upper pc:G ] ;
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221 tm:interval [ # the rest of the intervals on the circle of fifths
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222 ] .
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223 </pre>
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224 </div>
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225
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226 <p>A graphical representation of a similar description is shown in figure 2.
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227 We explicitly name the pitch classes involved in each interval on the circle of fifths.
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228 The IntervalDeviation concept describes the amount of deviation from a pure interval
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229 in terms of a specific type of comma and a corresponding value (a fraction of that comma).
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230 We can safely assume that a fifth is pure, unless the deviation is given.</p>
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231
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232 <p><center><img src="CircleOfFifths.png" alt="Using the Circle of Fifths to describe a temperament." width="350">
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233 <br><br>Figure 2. Describing temperaments using the circle of fifths.</center></p>
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234
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235
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236 <!-- ===================================================================== -->
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237
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238 <h2 id="reference">4. Cross-reference for Temperament classes and properties</h2>
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239
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240 <p>...</p>
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241
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242 <!-- The following is the script-generated list of classes and properties -->
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243 %s
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244 <!-- End of the terms list -->
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245
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246 <p>...</p>
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247
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248 <!-- ===================================================================== -->
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249
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250 <h2 id="references">A References</h2>
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251
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252 <dl>
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253 <dt class="label" id="ref-some">Music Ontology</dt>
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254 <dd><em>The <a href="http://purl.org/ontology/mo/">Music Ontology</a></em> is a thorough and mature ontology for describing
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255 music-related data, including musicological information. This ontology is intended to be
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256 used in conjunction with the Music Ontology.</dd>
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257 </dl>
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258
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259 <!--
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260 <h3 id="references-other">A.2 Other references</h3>
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261
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262 <dl>
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263 <dt class="label" id="ref-rfc2119">IETF RFC 2119</dt>
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264 <dd>
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265 <em><a href="http://www.ietf.org/rfc/rfc2119.txt">RFC 2119: Key words
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266 for use in RFCs to Indicate Requirement Levels</a></em>. Internet
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267 Engineering Task Force, 1997 (see http://www.ietf.org/rfc/rfc2119.txt).
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268 </dd>
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269 </dl>
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270 -->
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271
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272 <!-- ===================================================================== -->
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273
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274 <h2 id="changes">B Changes in this version (Non-Normative)</h2>
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275
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276 <ul>
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277 <li><p>first published draft 18-12-2009</p></li>
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278 </ul>
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279
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280 <h2><a id="acknowledgements"></a>C Acknowledgements (Non-Normative)</h2>
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281
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282 <p>Some modelling concepts in this ontology were borrowed form the
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283 <a href="http://purl.org/ontology/chord/">Chord Ontology</a></em>
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284 and the
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285 <a href="http://purl.org/ontology/similarity/">Music Similarity Ontology</a></em>.
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286 </p>
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287
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288 </body>
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289
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290 </html>
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291
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