Two voices per staff not rendered in parallel

[gregchapman-dev]

See attached MusicXML file: four vocal parts (two per staff). Musescore (and Finale) render them correctly, music21j renders them as if the two voices are interleaved as one voice, ending up with twice as many beats per measure as there should be.

Here's MuseScore (correct):

Here's music21j (not correct):

Here's the MusicXML file:

Processed-2.musicxml.txt

[gregchapman-dev]

If you give me a pointer or two, I'd be happy to work on this.

[gregchapman-dev]

@mscuthbert @jacobtylerwalls Interesting! It actually plays correctly in music21j, it's just the visual rendering that's weird.

[jacobtylerwalls]

Have you compared the result to the same thing without a grand staff?

[gregchapman-dev]

Hmmm... not sure how to do that in MusicXML. I tried deleting the <part-group> elements, changing this:

  <part-list>
    <part-group number="1" type="start">
      <group-symbol>bracket</group-symbol>
      <group-barline>no</group-barline>
    </part-group>
    <score-part id="P221c7a70916db2b49fc9794328148cc3">
      <part-name />
    </score-part>
    <score-part id="P4f3444e6d4f094bc75a62ea5a2d63b59">
      <part-name />
    </score-part>
    <part-group number="1" type="stop" />
  </part-list>

to this:

  <part-list>
    <score-part id="P221c7a70916db2b49fc9794328148cc3">
      <part-name />
    </score-part>
    <score-part id="P4f3444e6d4f094bc75a62ea5a2d63b59">
      <part-name />
    </score-part>
  </part-list>

and the resulting rendering weirdness was identical.

[gregchapman-dev]

Oh WAIT. It's not exactly the same. Still wrong, but the first measure is improved.

[gregchapman-dev]

@jacobtylerwalls, any pointers? I'd really like to fix this; this style of score is 90% of what my website will be displaying/messing with.

[jacobtylerwalls]

Sorry, I don't plan to debug it myself in the near term. I do wonder if comparing it to a fresh example composed in Musescore without grand staves would be illuminating (rather than hand-editing the musicxml).

[gregchapman-dev]

No worries, I will see what I can figure out.

[mscuthbert]

This is what I meant by the beta status. There's no one actively working on the project. Contributions are just coming as people need them for their own projects.

[gregchapman-dev]

Hmmm.... I dropped this same MusicXML file on the OSMD demo site (they parse the MusicXML and use VexFlow to display it), and it has the same bug! So I'm guessing this is actually a VexFlow issue. Yikes. I'll still try to figure it out, but I'll be focused in a different direction.

[mscuthbert]

btw -- multi-voice music does work in music21j -- I use it a lot.

[gregchapman-dev]

I'm sure that's true.

I think there is something weird about the scores I am creating that is triggering Vexflow misbehavior.

As mentioned above, the MusicXML renders fine in Musescore. I have also found that export to MEI (via converter21) renders fine with Verovio.

I'll get back to this in time. I'm distracted by some other projects at the moment.

[gregchapman-dev]

If you want to close this issue, that's ok with me. It really seems like it's either my bug or Vexflow's (or both), not music21j's.