Transpose after render changes result: Transposition to keys with more than 4 flats or sharps results in difficult sheets.

[fredrikvedvik]

We're having an issue where our sheets are rendered with a more difficult to read transcription than necessary when transposing the scores to a flat key. For example a sheet in E transposed to Db:

Manually written:

Output from OSDM (+9, with the source originally in E)

As we can see, E's for example are never notated, even though they also represent the same note as D#. Same with B's, making this a bit more difficult than necessary to read.

Is it possible to fix this?

[fredrikvedvik]

Here's an example file where that issue happens (originally in E, transposing for Eb instruments (+9) results in bad readability).

ID-98013_Det_er_en_skatt_bak_dekker_gjemt.musicxml.zip

[ammatwain]

Good morning Simon, I uploaded the MusicXML file to my test area at https://ammatwain.github.io/transport-calculator/, and it is transposed correctly.

[fredrikvedvik]

I fixed this for our case with a hardcoded if this then that solution

Basically, B-flats and E sharps can be written as just that instead of A-sharp and F-neutral, and it only occurred for those notes, so the issues we had are no longer to be seen.

I would revisit this if you wanted to implement something properly though, that fixes the root problem, not just the sideeffects.

[ammatwain]

Yes, Fredrik, my class works with equal temperament. The expected transposed note is delivered by the final link in a chain of key relationships.

[fredrikvedvik]

Oh now I see. Used the wrong transposition selector on your page 🙈

Your solution works great for this issue.

[ammatwain]

Darn it... I should have put it first!...

[sschmidTU]

Note that this problem doesn't occur when you transpose immediately before the first render(), after load():

        openSheetMusicDisplay.load(str).then(
            function () {
                // This gives you access to the osmd object in the console. Do not use in production code
                window.osmd = openSheetMusicDisplay;
                openSheetMusicDisplay.zoom = zoom;
                openSheetMusicDisplay.Sheet.Transpose = 9; // try transposing between load and first render if you have transpose issues with F# etc
                openSheetMusicDisplay.render();
                openSheetMusicDisplay.cursor.show();
            },
            function (e) {
                errorLoadingOrRenderingSheet(e, "rendering");
            }
        );

(modified code from our index.js, just adding the transpose)

So the issue here is changing the transpose after the first render, which can cause issues in some cases.
We haven't yet been able to figure out why.
But since load() is very fast, you should be able to simply load the sheet again and then transpose and render if you need transposition and the normal method causes issues.
So, this is a workaround for most cases. Of course it would be great to fix it completely though.