OMR File Conversion between musicxml, xml, and score using Ace Studio, Sound Slice and Verovio Humdrum

Sep 3

3 min read

We report a short study of OMR (optical music recognition) between .xml, .musicxml format and kern format. The conversion task involve three open source online web tools - Ace Studio, Sound Slice, and Verovio Humdrum. We show the result and compatibility of file conversion.

It is advantageous to use web based tools (as opposed to running from terminal on github open source codes). Here we discuss three tools, and compare their output results. We give the links to these tools at the end.

Musicxml, xml, and humdrum Kern conversion

The pipeline of conversion experiments

We first use this image of a music score as gold standard.

OMR conversion music xml by Stembay Learning Center — The original sound score sheet incipitis from Prelude in E Minor Op 28 No 4 of Chopin.

Using Ace Studio, the file is turned into a .musicxml file. One can rename it to .xml but it does not change. A screen shot of the musicxml file is below.

Musicxml file created with Ace Studio pdf to xml conversion tool.

The file is attached and uploaded.

Using Sound Slice, one can create a .xml file. A screenshot is shown below. Notice that two lines of header information are not included.

Image of musicxml file created by Sound Slice.

Sound Slice display the music score after conversion and compare to the original. Here is a screenshot.

Comparison of soundslice rendering to original music score. — OMR score comparison between original and sound slice conversion.

When this file is loaded to Verovio Humdrum, here is the output. The xml file has been reformatted.

When the .xml file created with sound slice is uploaded to Verovio humdrum, the rendering, xml file and original xml file are presented. — The .xml file converted from sound slice is uploaded to Verovio Humdrum.

By clicking the "convert to Humdrum", the file is instantly turned into kern format.

Verovio turned .xml file to .kern format but the .xml file must be from sound slice conversion. — When xml file from sound slice is uploaded, it can be converted to Kern Humdrum file. However, the .musicxml file converted from Ace Studio can not convert to kern in this interface.

Software control details

For the Verovio Humdrum, one can turn xml to kern by clicking the "convert to Humdrum".

In verovio humdrum, note the "convert to humdrum" button. — Location of the "convert to humdrum" button. It only worked for xml files created by Sound SLice, not Ace Studio.

Interface of Sound SLice software and score editting feature. — In Sound Slice one can edit the music note and save the results. The "save" button is located to upper right.

MUSICDIFF Results

We use MusicDiff software to compare three groups:

Group A: xml file created by Sound slice and then editted.
Group B: xml file created by Sound slice and musicxml file created by Ace Studio
Group C: xml file of editted file by Sound Slice to the Kern version.
Group D: Note musicdiff was not able to compare .abc file to .xml file.

Github at https://github.com/gregchapman-dev/musicdiff

Colab at (https://colab.research.google.com/drive/1JEb4EF-KmqbZt30t5OJ4i0-Fbvl5J5kY#scrollTo=f7tut1lPmGyL)

Group A results:

The differences are limited to the three tailored changes made intentionally and synthetically. This proves that when two .xml files are compared the difference distance is very accurate.

Stembay.org/omr musicdiff comparison of two files in .xml format. Three intentionally made edits are highlighted. Made by Alina Liu. — Musicdiff results of .xml file created in Sound slice to one editted (three noted moved) in Sound Slice. No other discrepancies were found.

Group B results:

Side by side results of musicxml file created by Ace Studio (left) and Sound Slice (right). Note all changes are artificial. It is likely different in xml format but they look the same after rendering (engraving). This shows although the formats are different the music is the same.

Stembay.org/omr musicdiff comparison of two xml files one made by using ace studio and another by sound slice. Made by Alina Liu. — MusicDiff comparison of results by Ace Studio (.musicxml) to Sound Slice (.xml). The two music pieces are essentially identical despite some differences (red) shown. These are only due to ambiguities.

Group C results:

It is shown that the kern file and xml file compare favorably. THough two instances of differences are highlighted (in red), these are

not musically different;
likely only a matter of notation synthax ambiguity.

Stembay.org/omr musicdiff comparison of two files in kern and .xml format. Made by Alina Liu. — The left (kern file) and right (xml file) compared by Musicdiff. The music is the same.

Conclusions

We can draw the following conclusions:

Ace Stuio and Sound Slice can both turn an image score to musicxml file. However, the file extensions are different.
1. The Ace Studio tool create a file with .musicxml extention.
2. The sound slice tool create a file with .xml extention.
Sound Slice allows the notes to be editted and saved, hence producing two xml files with tailor precise changes. This may be very handy in OMR studies.
Both the musicxml and xml files can be read by Verovio Humdrum. However, only the xml files created by Sound Slice can be converted to kern format in Verovio.
1. Note that the conversion may still be possible using github or terminal code runs.
2. Even when the .musicxml extension is changed to .xml, the Verovio Humdrum still can not convert to kern file.
Using musicdiff, we show that .xml and .kern files comparison of group truth to conversion are exactly identical.