Press n or j to go to the next uncovered block, b, p or k for the previous block.
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import { modelChords } from "../model/constraints2.js";
import { noteNames, chordGraph, chordName } from "../model/theory.js";
/**
* Step 2: chord-progression solving as shortest path of fixed length over the
* weighted chord graph G = (V, E, w); emits Roman-numeral progression + SVG.
* @implements {Step}
*/
export class Step2Chords extends Solvable(Step) {
/**
* @override
* @return {Promise<Object[]>} SCHEMA with the part.style preset options patched in.
*/
async schema() {
const presetOptions = ["manual"];
const presetLabels = ["Manual"];
try {
const resp = await fetch("scripts/presets/index.json");
const index = await resp.json();
for (const p of index) {
presetOptions.push(p.id);
presetLabels.push(`${p.name} (${p.works})`);
}
} catch {
console.warn("No preset index found, using manual only");
}
return SCHEMA.map((field) =>
field.name === "part"
? {
...field,
template: field.template.map((t) =>
t.name === "style"
? { ...t, options: presetOptions, labels: presetLabels }
: t,
),
}
: field,
);
}
/**
* @override
* Build chord-progression model, solve, render result with chord-graph data plus
* Roman-numeral progression (NC-filled when disabled, empty on UNSAT) and a concrete
* chord-name display string.
* @param {Object} parameters - Per-part form values; see {@link Step2Chords#schema}.
* @param {function(model: string): Promise<Object|null>} solver
* Pre-bound solver callback returning the MZN solution {path: number[], total_cost: number} or null.
* @return {Promise<Object>}
* Resolves to {textOutput, chordGraph: {graph, path, key, mode}, chords, concreteProgression};
* path is {nodes: string[], edges: Set<string>} on success, null otherwise.
*/
async solve(parameters, solver) {
const { key, mode, enable, preset, bars } = parameters;
const graph = chordGraph(mode, preset);
if (!enable) {
return {
textOutput: "Chord progression disabled.",
chordGraph: { graph, path: null, key, mode },
chords: Array(bars).fill("NC"),
concreteProgression: "",
};
}
const solution = await solver(modelChords(parameters, graph));
if (!solution) {
return {
textOutput: "No chord progression found.",
chordGraph: { graph, path: null, key, mode },
chords: [],
concreteProgression: "",
};
}
const pathNodes = solution.path.map((i) => graph.nodes[i - 1]);
const concreteNames = pathNodes.map((n) => chordName(n, key));
const pathEdges = new Set(
pathNodes.slice(0, -1).map((n, i) => `${n}->${pathNodes[i + 1]}`),
);
const labeled = pathNodes
.map((n, i) => `${n} (${concreteNames[i]})`)
.join(" -> ");
return {
textOutput: `Chord Progression Found:\n${labeled}\nTotal cost: ${solution.total_cost}`,
chordGraph: {
graph,
path: { nodes: pathNodes, edges: pathEdges },
key,
mode,
},
chords: pathNodes,
concreteProgression: concreteNames.join(" -> "),
};
}
}
/** @private */
const SCHEMA = (() => {
return [
{
name: "enable",
type: "bool",
label: "Enable",
tooltip: "Disable for atonal music without chord progression",
default: true,
ariaInvalid: "false",
},
{
name: "creativity",
type: "float",
label: "Creativity",
tooltip: "Higher values allow more unusual chord transitions",
default: 0.5,
min: 0,
max: 1,
step: 0.1,
showIf: "enable",
},
{
name: "part",
type: "nested",
label: "Part",
tooltip: "Editable in Step 1",
counter: "step1.parts",
showIf: "enable",
firstColumn: { type: "text", key: "label", readonly: true },
defaults: ["A", "B", "A", "C", "A"].map((label) => ({
key: label === "B" ? 7 : label === "C" ? 9 : 0,
mode: label === "C" ? "minor" : "major",
style: "manual",
start_chord: label === "C" ? "i" : "I",
end_chord: label === "B" ? "V" : label === "C" ? "V" : "I",
})),
template: [
{
name: "key",
type: "select",
label: "Key",
tooltip: "Tonal center for this part",
default: 0,
options: Array.from({ length: 12 }, (_, i) => i),
labels: noteNames(),
},
{
name: "mode",
type: "select",
label: "Mode",
tooltip: "Major or minor tonality",
default: "major",
options: ["major", "minor"],
labels: ["Major", "Minor"],
},
{
name: "style",
type: "select",
label: "Style",
tooltip: "Chord transition costs learned from analyzed works",
default: "manual",
options: ["manual"],
labels: ["Manual"],
},
{
name: "start_chord",
type: "select",
label: "Start Chord",
tooltip:
"First chord of the progression. The label (e.g. Dominant) shows the harmonic function",
default: "I",
dynamic: "chord",
},
{
name: "end_chord",
type: "select",
label: "End Chord",
tooltip:
"Last chord of the progression. I/i = resolved cadence, V = open half cadence",
default: "I",
dynamic: "chord",
},
],
},
];
})();
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