Each MusicXML part corresponds to a track in a Standard MIDI Format 1 file. The score-instrument elements are used when there are multiple instruments per track. The midi-device element is used to make a MIDI device or port assignment for the given track. Initial midi-instrument assignments may be made here as well.
The
<score-part>element.Each MusicXML part corresponds to a track in a Standard MIDI Format 1 file. The score-instrument elements are used when there are multiple instruments per track. The midi-device element is used to make a MIDI device or port assignment for the given track. Initial midi-instrument assignments may be made here as well.
See
https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/score-part/