Pedal bounces can have different forms all within one PedalMark spanner

[gregchapman-dev]

Motivation
I neglected to allow for this possibility in my recent PR that implemented pedal marks. See the attached PDF, where sometimes you see Ped Ped Ped * (all one PedalMark with the 2nd and 3rd Peds being SymbolAlt bounces) and sometimes you see Ped *Ped *Ped * (all one PedalMark, with the *Peds being Symbol bounces). That's fine, but there is one PedalMark, starting in the 4th measure of the top system on page 120 (page 18 of the PDF), that has 4 *Ped (Symbol) bounces, and then a Ped (SymbolAlt) bounce in the 6th measure of the top system on page 121 (page 19 of the PDF), before finally stopping with a *.

Proposed implementation
I need to add a pedalForm field to PedalBounce, so I can set each PedalBounce form appropriately, rather than the current method of using the enclosing PedalMark's pedalForm to note the form of all the bounces within the PedalMark.

Intent
[ ****] I plan on implementing this myself.
[ ] I am willing to pay to have this feature added.
[ ] I am starting a discussion with the hope that community members will volunteer their time to create this. I understand that individuals work on features of interest to them and that this feature may never be implemented.

sonata21-3.pdf

[gregchapman-dev]

@mscuthbert What do you think?

[mscuthbert]

Sorry -- I'm not enough in the piano pedal world (that's my wife's domain). What is the part of p. 120 that can't currently be represented, and what is the proposed solution? How would musicxml encode this?

[gregchapman-dev]

Unlike MusicXML, MEI can describe bounces that are not line-based. They can either be printed as "*Ped" (PedalForm.Symbol), or just as "Ped" (PedalForm.AltSymbol). When writing to MusicXML, since MusicXML only has line-based bounces, a PedalForm.Symbol bounce is written as a "stop" and then immediately "start" (i.e. "*Ped"), and a PedalForm.AltSymbol bounce is written as a "start" (i.e. "Ped"). And xmlToM21.py carefully reads those back in as bounces, not as individual starts and/or stops. That all works today in music21.

What doesn't work is when, within the span of a single (probably very long) PedalMark spanner, a score has both PedalForm.Symbol bounces ("*Ped") as well as PedalForm.AltSymbol bounces ("Ped"). This doesn't work because I only put a pedalForm property in the PedalMark spanner itself, because I assumed that all bounces within a given PedalMark spanner would have the same form. That assumption is not true (see attached PDF where there is a stretch of pedal marks that all end up in the same PedalMark spanner, but some of the bounces are "*Ped" and one is just "Ped"). So I need to use PedalMark.pedalForm as the default form for any bounces in the spanner, and allow for PedalBounce.pedalForm to override that.

Clear as mud? :-)

[mscuthbert]

OMG -- That is actually as clear as day and wow. Now I get it more, and understand some parts of your last PR that I didn't think I fully understood.

Since we've just got that PR, let's make it clearer:

Let's make FIVE pedal positions to have symbols

startForm: PedalForm
continueLine: PedalLine
bounceUp: PedalForm
bounceDown: PedalForm
endForm: PedalForm

new class PedalLine:

class PedalLine(common.StrEnum):
    NoLine = 'NoLine'  # default
    Line = 'Line'
    Dashed = 'Dashed'

and let's clarify PedalForm to have names closer to the shape:

class PedalForm(common.StrEnum):
    PedalName = 'PedalName'
    Ped = 'Ped'  # sometimes seen even for sost. etc.
    Star = 'Star'
    VerticalLine = 'VerticalLine'
    NoMark = 'NoMark'
    Caret = 'Caret'
    Inherit = 'Inherit'  # inherit from default/above. -- for now only useful on PedalObject...

(note: these being the first usages of CamelCase Enums, which I'm LOVING wish I had done long ago, let's make the enum values match the names in case and make that the new rule going forward....)

class PedalMark(spanner.Spanner):
    def __init__(
        self, 
        *spannedElements, 
        *, 
        pedalType: PedalType = PedalType.Sustain, 
        startForm: PedalForm = PedalForm.PedalName,
        continueLine: PedalLine = PedalLine.NoLine,
        bounceUp: PedalForm = PedalForm.Star,
        bounceDown: PedalForm = PedalForm.PedalName,
        endForm: PedalForm = PedalForm.Star,
        abbreviated: bool = False,
        **keywords
) -> None:
        super().__init__(*spannedElements, **keywords)
        from music21 import note
        self.fillElementTypes = [note.GeneralNote]

        self.pedalType: PedalType = pedalType
        
        self.startForm: PedalForm = startForm
        self.continueLine: PedalLine = continueLine
        self.bounceUp: PedalForm = bounceUp
        self.bounceDown: PedalForm = bounceDown
        self.endForm: PedalForm = endForm

        self.abbreviated: bool = abbreviated  # maybe make another PedalForm for this?
        self.placement: str|None = None


# later:
class PedalTransition(base.Music21Object):
       ... as before ...
       self.overrideForm: PedalForm = PedalForm.Inherit

Let's rename PedalObject. PedalTransition, since initial down and up might look like 'Ped.......*' but despite Ped, ....., and * looking like objects, none of those are PedalObjects currently. PedalTransition makes it clearer.

Thoughts? Now that I get what all this is about, even more excited!

[gregchapman-dev]

Oooh. Interesting. Let me take a shot at implementing it, and see what questions come up. (I definitely like the rename to PedalTransition for the reasons you give; I was feeling queasy about the PedalObject name, but couldn't figure out why.)

[gregchapman-dev]

Oh, I would like to have PedalForm.Unspecified = 'Unspecified' and PedalLine.Unspecified = 'Unspecified'. We can argue about when they should be used, but I think we need them in at least some cases.

[mscuthbert]

Oh, I would like to have PedalForm.Unspecified = 'Unspecified' and PedalLine.Unspecified = 'Unspecified'. We can argue about when they should be used, but I think we need them in at least some cases.

Great! Yes -- Unspecified as the norm, different from NoLine, etc.