MusicXML is a great effort to tackle a very difficult problem, but some of the details can get rather hairy (e.g. having to represent many concepts twice, once for the visual aspect, and once for the performance aspect; or how exactly to express incomplete slurs). Interoperability in practice seems to be fairly limited (Possibly because for many music programs, MusicXML import/export is an afterthought).

One of the biggest contributions a new standard could make is to provide as complete a test suite as possible of various musical concepts (and their corner cases!) and their canonical representation. It looks like MNX has already made good efforts in this direction.

Considering this data is machine-generated and machine-ingested, moving away from XML seems like a big step down.

[0] https://w3c.github.io/mnx/docs/comparisons/musicxml/

https://music-encoding.org/about/

This is what MuseScore 4 will soon start using.

Related: Can it handle non-Western notations?

Music notation is incredibly complex, and there are many places things can go wrong. There's a wide spectrum of error situations, such as:

* The exporting application "thinks" about notation in a different way than the importing application (i.e., it has a different mental model).

* MusicXML provides multiple ways of encoding the same musical concept, and some applications don't take the effort to check for all possible scenarios.

* Some applications support a certain type of notation while others don't.

* MusicXML doesn't have a semantic way of encoding certain musical concepts (leading applications to encode them as simple text (via the words element), if at all.

* Good ol' fashioned bugs in MusicXML import or export. (Music notation is complex, so it's easy to introduce bugs!)

Now as this song had nonsense lyrics and many repetitions and almost-repetitions, the structure of the song didn't quite pop out to me, so what I did was export a midi from vocaloid that I opened musescore. From musescore I then exported it as MusicXML. I opened that in Notepad++ for the sole purpose of pretty printing the xml to normalize the texual representation and saved it right back. I took that and opened it in a jupyter notebook where I scraped it for <measure> elements with regular expressions and then I searched for repeating ones, that I assembled into repeating segments and sub-segments.

This helped me memorize the song.

What I liked about MusicXML was that it was self-documenting enough that I didn't need to reference documentation and I could find candidates for normalization quite easy (for instance I didn't care about directions of stems or inferred dynamics).

A gotcha is that Musescore 4 has a bug where it doesn't show the "midi import" where you can adjust the duration quantization, this didn't matter to me for this song, but I did bite me once in the past when opening a midi from Vocaloid. Musescore 3 works. Without playing around with that there can be an issue where it infers 16th notes as staccato 8th notes and similar.