[Musicxml im-export] - New Transposition and pitches messed up

• Sep 23, 2019 - 13:58
Reported version
3.2
Type
Functional
Frequency
Many
Severity
S2 - Critical
Reproducibility
Always
Status
active
Regression
No
Workaround
No
Project

Hello,
When importing the attached file with instrument change from in D to in F, Musescore can have correct playback. But when exporting into Musicxml again, the transposition of the changed instrument is completely wrong, and the pitches are all messed up, some an octave higher or lower, sounding very terrible.

Regards
Haipeng

Attachment Size
changes.xml 20.37 KB

Comments

File changes.xml contains two transpose elements, diatonic -6 chromatic -10 in measure 1 and diatonic -4 chromatic -7 in measure 4. After saving to MusicXML by MuseScore, only one transpose is left: diatonic -4 chromatic -7 in measure 1.

Without further investigation I do not yet know what causes this, but my first guess would be that the MusicXML importer fails to associate the second transpose with the second instrument. In MusicXML transpose is a staff property, in MusicScore it is an instrument property.

Not only the import, as I can't see and do scores in Musescore, you can try to write some instrument changes with lots of major scales using Musescore alone, and do xml export. You will find:
1. the transpose of all changes will lost. Only the initial one is left;
2. There will be notes in wrong octave after the export.

Haipeng

Indeed on import only the first instrument's transposition is imported, on export only the first instrument's transposition is exported. Handling transposition for multiple instruments per staff has simply never been implemented.

For basically the same reasons as for #294814: [Musicxml im-export] - New Instrument name disappears, this issue is also definitely not trivial to solve. I do consider it more important that 294814, as it leads to very annoying information loss.

The most frustrating problem is not the transposition, but the pitches, some shifted an octave lower. Perhaps I must have someone enter an example in Musescore and open a new issue about that pitches for the export side.

Haipeng

Dear Leon,
Finally I got help from Mike320, and come up with a correct example showing the real problem I want to solve. The instrument names and abbreviations are correct, but besides the not exported second transposition, the most frustrating problem is the pitches of bar 4, where the note B is an octave higher when exported. There are too many such things, e.g., a F horn to Eb horn, when all C's are exported an octave lower. It's very strange why Musescore has such a mad behavior.

Haipeng
transposition

Attachment Size
clarinet_scales.mscz 5.28 KB
clarinet_scales.musicxml 9.63 KB

I don't understand anything about how MusicXML represents transposition, but I can say something about how these octave errors happen. For transpositing instrument, we usually store only a single representation of the pitch (a MIDI value that incorporates octave info), but two different values for the "TPC" (a numeric value indication used to differentiate, for example, D# from Eb). So for clarinet, say, we might store middle C as pitch 60, and the two TPC's as being the value for C and Bb if the 64 is meant to represent written pitch, or D and C and if the 60 was meant to indicate concert pitch. We calculate actual note to display from those pieces of data and checking whether we are in concert pitch mode or not.

Then If somehow the wrong MIDI pitch or TPC's get recorded in the file, or they are created incorrectly based on incorrect interpretation of the info on import, then the algorithm that tries to calculate the note from the info I mentioned (one MIDI pitch and two TPC's) will often produce an incorrect octave. We've fixed a nuber of bugs with that type of symptom over the eyars having nothing to do with MusicXML.

So I'm guessing that's what is going on here. Somehow, we either write the MusicXML info wrong or read it wrong, such that by the time we try to construct the note from what we believe to be the MIDI pitch and the two TPC's, one or more of those values is off, and we get the wrong answer. But I don't understand enough about how the info is supposed to be represented in MusicXML in order to say more.

I note that the same thing happens in 2.3.2, BTW. I implemented much of the code having to do with transposition of instrument changes back around 2.1, and I have no trouble believe I didn't handle MusicXML correctly. But I don't know if the problem is on the export or import side.

There are indeed (at least) two different issues here
- only the first transpose is imported/exported from/to MusicXML (working on that)
- sometimes something in the pitch calculations breaks
The first issue I know how to solve, the second one I still need to investigate.
Mike, Haipeng, thanks for the example. Do you know where the issue originates (import or export, i.e. is the MusicMXL file produced by MuseScore correct) ? Could you produce the same example using one of our competitors ?

Additional remark: the second issue may be a side effect of the first issue (as the transposition for the second instrument is incorrect, pitch calculations may fail). Do you also see the pitch issue for a file with a single instrument ?

Dear Leon,
The problem only appears when there's an instrument change with different transposition setting. A staff with only one transposed instrument will never have pitch issue. The last example was an original Musescore engraving and I produced the xml file using the latest nightly build. Using other softwares like Finale and Sibelius to do such changes will never have such a strange issue, and the second and other consequent transposition settings will all be included.

Haipeng

Manually fixed file clarinet scales (using an editor), it now imports correctly into Finale Notepad (the only competition I have available). Two changes were required: adding a transpose element for the second instrument and fixing a note that was exported one octave off. Thus it seems we are on the right track towards fixing this issue, it looks like multiple issues will have to be fixed. Does this file works as expected for you ?

Attachment Size
clarinet_scales_xml_fixed.musicxml 9.74 KB