RepeatBrackets are not applied to the second (left-hand) staff in piano scores from MusicXML.

[seffka]

music21 version

9.3.0

Operating System(s) checked
macOS Sequoia 15.5

Problem summary

If a piano score MusicXML contains a single part with two staffs, music21 represents
it as a two part score. If the MusicXML contains repeats with various endings,
they are converted to RepeatBracket objects, but added only to the first part.

As a result, music21 produce corrupted expanded version of the score (e.g., 8 bars in the right hand, and 10 in the lefthand).

Steps to reproduce

import music21

s = music21.converter.parse("example.xml")

print("Part 0----------------")
for e in s.parts[0].flat.getElementsByClass(music21.spanner.RepeatBracket):
    print(e)
print("----------------------")

print("Part 1----------------")
for e in s.parts[1].flat.getElementsByClass(music21.spanner.RepeatBracket):
    print(e)
print("----------------------")

expanded = s.expandRepeats()
measures_in_parts = [[measure for measure in part.getElementsByClass(music21.stream.Measure)] for part in expanded.parts]

print(f"Measures in expanded part#0: {len(measures_in_parts[0])}\nMeasures in expanded part#1: {len(measures_in_parts[1])}")

Expected vs. actual behavior
There should be identical output for Part#0 and Part#1: two RepeatBrackets, 8 bars when expanded.

More information

example.xml

[mscuthbert]

Thank you for the super clear problem description. Will try to fix when I have time. Also happy to review patch requests. Thanks!

[mscuthbert]

Great -- I can confirm that there are several bugs / features that we don't currently implement, but I think they are fixed by one fix:

• RepeatBrackets are only written on one staff of a piano part, but they apply to all parts. We should be putting them into each part on parsing, but use hideObjectOnPrint=True to not include them.

it would be a big help to me if you could make the simplest uncompressed musicxml file that still shows the problem -- one note per measure, no slurs, etc. -- I am going to need to step through all the elements of parsing many times and not having to skip over notes that are irrelevant to the problem is a big help.

[mscuthbert]

Hi -- just pinging again if you could make the simplest fix version that'd be a great help!

[seffka]

Hi! My colleague is preparing the simplified example and will upload it soon. We'll see if we could fix the bug itself.

[OttavioCresos]

Hello Michael and Seva, sorry for the wait. Here is the simplest example ever, one note per measure. Please let me know if you need any mods. And of course, thank you Michael for having a look!

exampleMusescore.xml

[mscuthbert]

Wonderful! I can commit to working on this by the weekend.

[mscuthbert]

Narrowed problem down to import -- if I insert identical repeat brackets in the second part then the repeat brackets are honored as properly formed in other software (like MuseScore 3 + 4)

s = converter.parse('~/Downloads/exampleMusescore.xml')
s.parts[1].insert(0, spanner.RepeatBracket(s.parts[1][stream.Measure][1], number=1))
s.parts[1].insert(0, spanner.RepeatBracket(s.parts[1][stream.Measure][2], number=2))
s.show()

on to fixing import.

[seffka]

Great news! Huge thanks to @mscuthbert for developing and sharing such an incredible project!