Esempi musicali in MEI con apparato critico nelle note

// ═══ Postext Cookbook · Nº 165 · MEI music examples with a critical apparatus ═════
// https://postext.dev/en/cookbook/musicology-mei-apparatus
// Code: MIT · Text: original (CC BY 4.0) · Music: Sumer is icumen in, after Rockstro (PD)
// Fonts: Crimson Pro, Cormorant Garamond, Source Sans 3 (SIL OFL 1.1) · Needs postext ≥ 1.54.0
import {
  buildDocumentWithFonts, renderPageToCanvas, initMusicEngine,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'en'; // @lang: the language of the sample document ('en' | 'es')
const RECIPE = 'musicology-mei-apparatus';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: a rubric red for kickers, labels and the notes' rule; ink on cream
const palette = {
  ink: '#211d1a', // text and notation: a warm near-black
  rubric: '#8c2f1f', // the one accent, the red of the manuscript's rubrics
  muted: '#6c645b', // running heads, colophon
  rule: '#cbbfae', // hairlines
  paper: '#fcfaf6',
};
// col(id): a colour linked to its palette entry, with the entry's hex beside the id.
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = [
  ...Object.entries(palette).map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } })),
  // The engine's defaults link to main-color: point it at the accent, never the default blue.
  { id: 'main-color', name: 'accent (defaults)', value: { hex: palette.rubric, model: 'hex' } },
];
// #endregion
const MARGIN = { top: 22, bottom: 22, inner: 19, outer: 21 }; // 156 × 234 mm, mirrored
const LEAD = 14.5; // body leading in pt: the baseline grid
const at = (to, edge, x = 0, y = 0) => ({ anchor: { to, edge }, offset: { x: mm(x), y: mm(y) } });
const label = { fontFamily: 'Source Sans 3', fontWeight: 600, textTransform: 'uppercase' };

// #region answer: MEI examples engraved in the text, their apparatus in footnotes
// In the Markdown each example is a ```mei fence. A variant is encoded where it stands,
// <app><lem>…</lem><rdg source="#Hw #Bu">…</rdg></app>: the staff shows the lemma, and
// the file keeps the reading for anyone who opens the encoding. The apparatus entry is a
// footnote cited from the paragraph that discusses the bar: `[^b40]: **b. 40, n. 2** A ] G`.
const scoreStyle = {
  staffSize: mm(5), // running-text examples: 4.5–5.5 mm
  musicFont: 'Leipzig', // lighter than Bravura, close to a 19th-century plate
  textFont: 'Crimson Pro', // the underlay in the book's own face
  barNumbers: 'system', // the apparatus is keyed by bar: number every system
  spacing: 0.95,
  systemGap: mm(4),
  marginTop: pt(4),
  marginBottom: pt(LEAD / 2),