MusicXML accidental support

This is a documentation of the current state of MusicXML accidental support in OSMD, based on the currently used VexFlow version. The end goal is to support all MusicXML accidentals.

MusicXML	OSMD	SMuFL class / glyph	VexFlow 1.2.93	Notes
sharp	SHARP	accidentalsStandard / accidentalSharp	#
natural	NATURAL	accidentalsStandard / accidentalNatural	n
flat	FLAT	accidentalsStandard / accidentalFlat	b
double-sharp	DOUBLESHARP	accidentalsStandard / accidentalDoubleSharp	##
sharp-sharp		accidentalsStandard / accidentalSharpSharp		TBD Verify if concatenation of accidentals is feasible
flat-flat	DOUBLEFLAT	accidentalsStandard / accidentalDoubleFlat	bb	OSMD also recognizes value double-flat which is absent from MusicXML
natural-sharp		accidentalsStandard / accidentalNaturalSharp		TBD Verify if concatenation of accidentals is feasible
natural-flat		accidentalsStandard / accidentalNaturalFlat		TBD Verify if concatenation of accidentals is feasible
triple-sharp	TRIPLESHARP	accidentalsStandard / accidentalTripleSharp	###
triple-flat	TRIPLEFLAT	accidentalsStandard / accidentalTripleFlat	bbs	OSMD’s TRIPLEFLAT uses a VexFlow accidental that is different than the one encoded in MusicXML. TBD Verify if concatenation of accidentals is feasible
quarter-flat	QUARTERTONEFLAT	accidentalsSteinZimmermann / accidentalQuarterToneFlatStein OR accidentalsAEU / accidentalKomaFlat	d	The interval values are different because Stein-Zimmerman is 24-TET and AEU (Turkish) is 53-TET
quarter-sharp	QUARTERTONESHARP	accidentalsSteinZimmermann / accidentalQuarterToneSharpStein OR accidentalsAEU / accidentalKomaSharp	+	The interval values are different because Stein-Zimmerman is 24-TET and AEU (Turkish) is 53-TET
three-quarters-flat	THREEQUARTERSFLAT	accidentalsSteinZimmermann / accidentalThreeQuarterTonesFlatZimmermann	db
three-quarters-sharp	THREEQUARTERSSHARP	accidentalsSteinZimmermann / accidentalThreeQuarterTonesSharpZimmermann	++
slash-quarter-sharp	SLASHQUARTERSHARP	accidentalsAEU / accidentalKucukMucennebSharp	±
slash-sharp	SLASHSHARP	accidentalsAEU / accidentalBuyukMucennebSharp	+±
slash-flat	SLASHFLAT	accidentalsAEU / accidentalBakiyeFlat	bs
double-slash-flat	DOUBLESLASHFLAT	accidentalsAEU / accidentalBuyukMucennebFlat	bss
sharp-down
sharp-up
natural-down
natural-up
flat-down
flat-up
double-sharp-down
double-sharp-up
flat-flat-down
flat-flat-up
arrow-down
arrow-up
sharp-1
sharp-2
sharp-3
sharp-5
flat-1
flat-2
flat-3
flat-4
sori	SORI	accidentalsPersian / accidentalSori	o
koron	KORON	accidentalsPersian / accidentalKoron	k
other				Fallback to smufl attribute which specifies an explicit SMuFL glyph name
-	-	-	ashs	VexFlow’s Arabic-Sharp-Half-Sharp is not encoded in MusicXML nor in SMuFL
-	-	-	afhf	VexFlow’s Arabic-Flat-Half-Flat is not encoded in MusicXML nor in SMuFL

[infojunkie]

Updated table with fix above 🎉

[infojunkie]

Regarding the alter value of the accidentals, this is where things get complicated 😅 In a nutshell, different accidentals refer to different tuning systems and/or different notation systems (these are 2 different things), which may end up with overlapping intervals and therefore overlapping accidentals.

For example, quarter-flat in Stein-Zimmermann notation has the same value as flat-up in Gould arrow notation and slash-flat in Arabic notation (all of which are actual MusicXML accidental values).

Same for different accidentals representing quarter-sharp in different systems.