title: MusicXML file not playing - something missing?
body: <p>I have generated this musicXML file with my own C++ code. It displays ok in musescore etc, but it is not playing. I am guessing some important info is missing in the file? </p>
  
  <p>Here is the file: <a href="https://dl.dropboxusercontent.com/u/13564139/cf.xml" rel="nofollow">https://dl.dropboxusercontent.com/u/13564139/cf.xml</a></p>
  
  <p>This is the beginning:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8" standalone="no"?&gt;
  &lt;!DOCTYPE score-partwise PUBLIC
  "-//Recordare//DTD MusicXML 2.0 Partwise//EN"
  "http://www.musicxml.org/dtds/partwise.dtd"&gt;
  &lt;score-partwise version="2.0"&gt;&lt;work&gt;
  &lt;work-title&gt;Generated Music&lt;/work-title&gt;&lt;/work&gt;&lt;identification&gt;
  &lt;creator type="composer"&gt;Optimuse&lt;/creator&gt;&lt;/identification&gt;&lt;part-list&gt;
  &lt;score-part id="P2"&gt;
  &lt;part-name&gt;Part 1&lt;/part-name&gt;
  &lt;/score-part&gt;
  &lt;score-part id="P1"&gt;
  &lt;part-name&gt;Part 2&lt;/part-name&gt;
  &lt;/score-part&gt;
  &lt;/part-list&gt;
  &lt;part id="P2"&gt;
  &lt;score-instrument id="P2"&gt;
  &lt;instrument-name&gt;Violin&lt;/instrument-name&gt;&lt;/score-instrument&gt;
  &lt;midi-instrument id="P1"&gt;
  &lt;midi-channel&gt;1&lt;/midi-channel&gt;
  &lt;midi-program&gt;1&lt;/midi-program&gt;
  &lt;volume&gt;80&lt;/volume&gt;
  &lt;pan&gt;0&lt;/pan&gt;&lt;/midi-instrument&gt; &lt;measure number="1"&gt;&lt;attributes&gt;&lt;divisions&gt;4&lt;/divisions&gt;&lt;key&gt;&lt;fifths&gt;-4&lt;/fifths&gt;&lt;mode&gt;minor&lt;/mode&gt;&lt;/key&gt;&lt;time&gt;&lt;beats&gt;4&lt;/beats&gt;&lt;beat-type&gt;4&lt;/beat-type&gt;&lt;/time&gt;&lt;clef&gt;&lt;sign&gt;G&lt;/sign&gt;&lt;line&gt;2&lt;/line&gt;&lt;/clef&gt;&lt;/attributes&gt;
  &lt;note&gt;
  &lt;rest/&gt;&lt;duration&gt;8&lt;/duration&gt;
  &lt;type&gt;half&lt;/type&gt;&lt;stem&gt;up&lt;/stem&gt;
  &lt;/note&gt;
  
  &lt;note&gt;
  &lt;pitch&gt;
  &lt;step&gt;D&lt;/step&gt;&lt;alter&gt;-1&lt;/alter&gt;
  &lt;octave&gt;5&lt;/octave&gt;
  &lt;/pitch&gt;
  &lt;duration&gt;8&lt;/duration&gt;
  &lt;type&gt;half&lt;/type&gt;&lt;stem&gt;down&lt;/stem&gt;
  &lt;accidental&gt;flat&lt;/accidental&gt;
  &lt;/note&gt;
  &lt;/measure&gt;
  &lt;measure&gt;
  &lt;note&gt;
  &lt;pitch&gt;
  &lt;step&gt;E&lt;/step&gt;&lt;alter&gt;-1&lt;/alter&gt;
  &lt;octave&gt;5&lt;/octave&gt;
  &lt;/pitch&gt;
  &lt;duration&gt;4&lt;/duration&gt;
  &lt;type&gt;quarter&lt;/type&gt;&lt;stem&gt;down&lt;/stem&gt;
  &lt;accidental&gt;flat&lt;/accidental&gt;
  &lt;/note&gt;
  </code></pre>