@typedin/music-utilities/dist/scale-builders/ScaleBuilder.js

A set of resources and modules I use to develop music applications.

import { spanOver } from "./spanOver.js";
import { intervalBuilders } from "../interval-builders/index.js";
// INFO go see the type declaration
//
// Key Elements of a Scale:
//
// Tonic (Root Note) – The starting note that gives the scale its name.
// Intervals – The pattern of whole steps (W) and half steps (H) that determine the character of the scale.
// Octave Structure – Most scales repeat every octave (e.g., C–D–E–F–G–A–B–C).
// Mode or Type – Scales can be major, minor, modal, or exotic, based on their interval patterns.
// Number of Notes – Common scales have 5 (pentatonic), 7 (heptatonic), or even 12 (chromatic) notes.
export const ScaleBuilder = function (tonic, scaleSchema, number_of_octaves = 1) {
    this.tonic = tonic;
    this.scaleSchema = scaleSchema;
    this.tonicRepetition = true;
    this.withoutTonicRepetition = () => {
        this.tonicRepetition = false;
        return this;
    };
    this.scale = () => {
        // this create a scale with 7 notes
        let result = scaleSchema.map((element, index) => {
            const note = intervalBuilders
                .find((intervalBuilder) => intervalBuilder.name == element.interval)
                ?.callable(tonic);
            return {
                ...note,
                order: index + 1,
                degree: index + 1,
                function: element.function,
            };
        });
        // spanOver creates many scales with the repetition of the tonic
        // for example: 2 octaves in C Major
        // we will have 3 tonics
        if (number_of_octaves > 1) {
            result = spanOver(result, number_of_octaves);
            result.pop();
        }
        if (this.tonicRepetition) {
            result.push({
                ...tonic,
                octave: tonic.octave + number_of_octaves,
            });
        }
        return result;
    };
};
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