Updates:
Status: Invalid
Comment #1 on issue 2564 by [email protected]: MuseScore MusicXML
interoperability with musicxml2ly
http://code.google.com/p/lilypond/issues/detail?id=2564
It's an error in the XML from musescore, based on an error in the original
Musescore scoring, it would appear. Lilypond is actually doing a good job
of showing this up. From that XML, a correct pitched rest:
<rest>
<display-step>A</display-step>
<display-octave>5</display-octave>
</rest>
Now the error:
<rest>
<display-step>B</display-step>
<display-octave>22</display-octave>
</rest>