The term 'layer' is used instead of 'voice' in order to avoid confusion between 'voice' and 'voice leading' and 'voicing'. The def attribute may be used to create a connection with a layerDef element where logical and visual information about the layer is recorded. Alternatively, the n attribute may be used as a reference to a layerDef element with the same value in its n attribute. If neither def nor n attributes are present, then encoding order of the layers is presumed to match the encoding order of the layer definitions.
                     <elementSpec ident="layer" module="MEI.shared">
                        
                        <desc>An independent stream of events on a staff.</desc>
                        
                        <classes>
                           
                           <memberOf
                                 key="att.basic"/>
                           
                           <memberOf
                                 key="att.facsimile"/>
                           
                           <memberOf
                                 key="att.labelled"/>
                           
                           <memberOf
                                 key="att.linking"/>
                           
                           <memberOf
                                 key="att.metadataPointing"/>
                           
                           <memberOf
                                 key="att.nInteger"/>
                           
                           <memberOf
                                 key="att.responsibility"/>
                           
                           <memberOf
                                 key="att.typed"/>
                           
                           <memberOf
                                 key="att.layer.log"/>
                           
                           <memberOf
                                 key="att.layer.vis"/>
                           
                           <memberOf
                                 key="att.layer.ges"/>
                           
                           <memberOf
                                 key="att.layer.anl"/>
                           
                           <memberOf
                                 key="model.layerLike"/>
                           </classes>
                        
                        <content>
                           
                           <rng:zeroOrMore>
                              
                              <rng:choice>
                                 
                                 <rng:ref
                                       
                                       name="model.annotLike"
                                       />
                                 
                                 <rng:ref
                                       
                                       name="model.appLike"
                                       />
                                 
                                 <rng:ref
                                       
                                       name="model.editLike"
                                       />
                                 
                                 <rng:ref
                                       
                                       name="model.graphicPrimitiveLike"
                                       />
                                 
                                 <rng:ref
                                       
                                       name="model.layerPart"
                                       />
                                 
                                 <rng:ref
                                       
                                       name="model.milestoneLike.music"
                                       />
                                 
                                 <rng:ref
                                       
                                       name="model.transcriptionLike"
                                       />
                                 </rng:choice>
                              </rng:zeroOrMore>
                           </content>
                        
                        <remarks>
                           
                           <p part="N">The term 'layer' is used instead of 'voice' in order to avoid confusion between 'voice'
                              and
                              'voice leading' and 'voicing'. The 
                              <att scheme="TEI">def</att> attribute may be used to create a
                              connection with a 
                              <gi scheme="MEI">layerDef</gi> element where logical and visual
                              information about the layer is recorded. Alternatively, the 
                              <att scheme="TEI">n</att> attribute may be
                              used as a reference to a 
                              <gi scheme="MEI">layerDef</gi> element with the same value in its
                              
                              <att scheme="TEI">n</att> attribute. If neither 
                              <att scheme="TEI">def</att> nor 
                              <att scheme="TEI">n</att> attributes are present,
                              then encoding order of the layers is presumed to match the encoding order of the layer
                              definitions.</p>
                           </remarks>
                        </elementSpec>