I can't reproduce your results. I tried to put your XML into hello2.xml and compile it. But it produced pdf with the same error, Your lilypond file is compiling correctly for me. Can you try my xml? Is anything wrong with it? My lilypond version is 2.22.1.
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE score-partwise PUBLIC
"-//Recordare//DTD MusicXML 4.0 Partwise//EN"
"http://www.musicxml.org/dtds/partwise.dtd";>
<score-partwise version="4.0">
<part-list>
<score-part id="P1">
<part-name>Music</part-name>
<score-instrument id="Piano">
<instrument-name>Piano</instrument-name>
</score-instrument>
</score-part>
</part-list>
<part id="P1">
<measure number="1">
<attributes>
<divisions>1</divisions>
<key>
<fifths>1</fifths>
</key>
<time>
<beats>2</beats>
<beat-type>4</beat-type>
</time>
<staves>2</staves>
<clef number="1">
<sign>G</sign>
<line>2</line>
</clef>
<clef number="2">
<sign>F</sign>
<line>4</line>
</clef>
</attributes>
<note>
<pitch>
<step>C</step>
<alter>0</alter>
<octave>4</octave>
</pitch>
<duration>2</duration>
<type>half</type>
<staff>1</staff>
</note>
<backup>
<duration>2</duration>
</backup>
<note>
<pitch>
<step>D</step>
<alter>0</alter>
<octave>3</octave>
</pitch>
<duration>2</duration>
<type>half</type>
<staff>2</staff>
</note>
</measure>
</part>
</score-partwise>
\version "2.22.1" % automatically converted by musicxml2ly from ./hello2.xml \pointAndClickOff
\header {
}
\layout {
\context { \Score
autoBeaming = ##f
}
}
PartPOneVoiceOne = \relative c' {
\clef "treble" \time 2/4 \key g \major | % 1
<c d,>2 \change Staff="2" }
% The score definition
\score {
<<
\new PianoStaff
<<
\set PianoStaff.instrumentName = "Music"
\context Staff = "1" <<
\mergeDifferentlyDottedOn\mergeDifferentlyHeadedOn
\context Voice = "PartPOneVoiceOne" { \PartPOneVoiceOne }
>> \context Staff = "2" <<
\mergeDifferentlyDottedOn\mergeDifferentlyHeadedOn
>>
>>
>>
\layout {}
% To create MIDI output, uncomment the following line:
% \midi {\tempo 4 = 100 }
}
hello2.pdf
Description: Adobe PDF document
