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MusicXML import doesn't read `<midi-instrument>` changes in `<sound>`

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Issue 类型
缺陷
描述清晰度
基本清楚
活跃度
活跃
技术栈
python
领域
backend

调研方向

Start with SoundTagMixin.setSound in musicxml/xmlSoundParser.py, which currently handles only tempo, and with where the importer reads midi-instrument from score-part. Reproduce with the XML in the issue and check whether a sound inside a measure or direction is reached at all. The issue leaves open whether the change should become a new Instrument or another record, so settle that with the maintainers first. Done means the example yields program 73 at offset 4.0 and the related score-instrument case (#1696) is not made worse.

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描述

music21 version

10.5.0

Problem summary

A <sound> element can contain a <midi-instrument> that changes a part's program partway through, for example a doubler switching from violin to flute. The importer only reads <midi-instrument> from the <score-part>, so the whole part keeps its first program.

Steps to reproduce

from music21 import converter, instrument

xml = '''<score-partwise version="4.0">
  <part-list><score-part id="P1"><part-name>Music</part-name>
    <score-instrument id="P1-I1"><instrument-name>Doubler</instrument-name></score-instrument>
    <midi-instrument id="P1-I1"><midi-program>41</midi-program></midi-instrument>
  </score-part></part-list>
  <part id="P1">
    <measure number="1">
      <attributes><divisions>1</divisions></attributes>
      <note><pitch><step>C</step><octave>4</octave></pitch><duration>4</duration><type>whole</type></note>
    </measure>
    <measure number="2">
      <sound><midi-instrument id="P1-I1"><midi-program>74</midi-program></midi-instrument></sound>
      <note><pitch><step>D</step><octave>4</octave></pitch><duration>4</duration><type>whole</type></note>
    </measure>
  </part>
</score-partwise>'''

parsed = converter.parse(xml, format='musicxml')
print([(float(i.getOffsetInHierarchy(parsed)), i.instrumentName, i.midiProgram)
       for i in parsed.recurse().getElementsByClass(instrument.Instrument)])

Expected vs. actual behavior

Expected a second instrument, or some other record of the change, with program 73 at offset 4.0. Actual:

[(0.0, 'Doubler', 40)]

More information

Exporters usually write the change inside a direction, next to the printed cue, for example <direction><direction-type><words>Flute</words></direction-type><sound><midi-instrument id="P1-I1"><midi-program>74</midi-program></midi-instrument></sound></direction>. That's ignored too: SoundTagMixin.setSound in musicxml/xmlSoundParser.py only handles tempo.

Related: #1696, where the importer only reads a part's first <score-instrument>. Both are ways MusicXML encodes an instrument change partway through a part.

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