Add mensuralBlackFusa glyph to close gap in 'Medieval and Renaissance individual notes' range

[dspreadbury]

Originally reported in steinbergmedia/bravura#12

The Unicode Musical Symbols block's MUSICAL SYMBOL FUSA BLACK (U+1D1C0) currently maps, in Bravura, to the exact same glyph as MUSICAL SYMBOL SEMIMINIMA BLACK (U+1D1BE): both reference mensuralBlackSemiminima (U+E955). This isn't a mapping bug that can be fixed by repointing a reference, because SMuFL doesn't define a mensuralBlackFusa glyph at all.

To address this, we should add mensuralBlackFusa to the 'Medieval and Renaissance individual notes' range.

[dspreadbury]

Do you agree with the proposed approach here @mscuthbert?

[mscuthbert]

Shortest Answer: U+1D1C0 should render as a note with a filled diamond head and two flags. This note should be added to SMuFL as mensuralWhiteSemifusa NOT mensuralBlackFusa. The Unicode glyph name is incorrect.

Short answer: not fully on board -- but it's complex -- read when you have mindspace. I didn't put all this into the original SMuFL proposal, for fear that the overcomplexity would result in a "Screw that..." and it's go the way of Woodwind Fingerings.

---

A lot of Perry's proposals for the Medieval and Renaissance area are based on creating things that "should have existed by analogy" but didn't in reality. Putting the reference engraving here for analogy:

(I'll use the terms "void" and "filled" for graphical representation and "White" and "Black" for the systems)

Everything here is designed to look good in the engraving of what's called "White Mensural Notation" (dominant 1450-1630ish) where the default symbols for Maxima, Longa, Brevis, Semibrevis, and Minima were void. Filled symbols in for Maxima, Longa, Brevis, and Semibrevis (and sometimes also Minima) indicate an alternative interpretation -- usually triplets in simple time; in what we'd call compound time they sometimes mean quadruplets; sometimes they mean a second voice in the same staff -- anything but the "main interpretation". Smaller than a Minim, there were two ways to write the next two levels down. A semiminima can either be written as a filled version of the minim (most common) or adding a flag to the void minima. The fusa adds a(nother) flag to whatever form the copyist/tradition used for semiminima. The rare semifusa both traditions seem to have agreed that you put two flags on a filled note. Here's from Apel:

Then there's black notation (Medieval, dominant 1250-1450) which (in simple terms) used filled Maxima, longa, brevis, semibrevis, minim to mean standard notes and void (or filled-red) maxima, longa, brevis, semibrevis (and sometimes minima) to mean alternate interpretations like tuplets, or quadruplets, or other voices. (Let's not get to semiminims etc. for now)

To match the look of original manuscripts or prints White notation is usually engraved with serifs on the noteheads whether filled or void, and black notation is engraved without whether filled or void (compare U+E933 (W) to U+E931 (B) or U+E93C (W) to U+E939 (B)). I and other early music folk use these small visual differences to know whether a passage that is void is a bunch of normal notes in white notation or triplets in black notation.

--
Now look again at what is in Mensural notes in Unicode -- everything there is to support White (Renaissance) notation, but it lacks a lot of the system, and (SMuFL has gaps too).

Long notes in White notation:

Unicode has no filled symbols for Maxima, Longa, Brevis.

SMuFL also lacks these characters in white notation (as notes or noteheads), but users can get by using the Black notation symbols. Ideally SMuFL would add filled serif versions of U+E933 and U+E937 (no need for filled U+E93C since U+E93D is that). The names of noteheads are a bit unhelpful -- so I'm just ignoring them for now.

Shorter notes in white notation

Start from the bottom and immediately see the errors in the Unicode system: 1D1C0 is a semifusa not "Fusa Black". The two systems in white mensural notation to represent a fusa are 1D1BF (correctly called Fusa White, though we should say FusaVoid) or 1D1BE (called Seminima Black). The two systems to represent a seminima are either 1D1BD (correctly called Seminima White (=Void)) or 1D1BC (MinimaBlack). So 1D1BC and 1D1BD can represent the same note value OR alternative representations of two different note values.

It is probably too late to add all of these complexities to SMuFL, but we can see what common composed note forms are missing in White notation quite easily from here:

need
a void note with a flag (going right) which looks equivalent to 1D1BD and is an alternative way of expressing the value of mensuralWhiteSemiminima (call it mensuralWhiteSemiminimaVoidFlag ?)

a void note with two flags (going right) which looks equivalent to 1D1BF and is an alternative way of expressing the value of mensuralWhiteFusa (call it mensuralWhiteFusaVoid2Flag ?)

a filled note with two flags (going right) which looks equivalent to 1D1C0 but is called mensuralWhiteSemifusa.

hope that that clears up a little bit! Sorry so complex. I'm just the messenger! But it does represent 400+ years of musical evolution, so we've done just as much change since 1650 too! I'll fill in separate issues for other things that I've noticed over time.