mirror of
https://codeberg.org/uzu/strudel
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robmckinnon
99 lines
3.5 KiB
JavaScript
99 lines
3.5 KiB
JavaScript
/*
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pitches.mjs - defines Pitches for equal division of the octave (EDO) scale
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- Port of pitfalls/lib/Pitches.lua - see <https://github.com/robmckinnon/pitfalls/blob/main/lib/Pitches.lua>
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Copyright (C) 2025 Rob McKinnon and Strudel contributors - see <https://codeberg.org/uzu/strudel/src/branch/main/packages/edo/pitches.mjs>
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This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details. You should have received a copy of the GNU Affero General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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function ratio(division, edivisions) {
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return division === 0 ? 1 : Math.pow(2, division / edivisions);
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}
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// This function gets frequency based on index, edo, octave, and base frequency
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function get_freq(base_freq, edo, index, oct, base_octave) {
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let f = base_freq * ratio(index - 1, edo);
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if (oct < base_octave) {
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f /= Math.pow(2, base_octave - oct);
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} else if (oct > base_octave) {
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f *= Math.pow(2, oct - base_octave);
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}
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return f;
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}
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// Convert MIDI number to Hz using a given tuning multiplier
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function midi_to_hz(n, tuning) {
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return tuning * Math.pow(2, (n - 69) / 12.0);
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}
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const denom = Math.log(2);
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function hz_to_midi(freq, tuning) {
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return 12.0 * (Math.log(freq / tuning) / denom) + 69;
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}
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export class Pitches {
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constructor(scale, intervals, tuning, midi_start, root_octave) {
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this.scale = scale;
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this.intervals = intervals;
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this.base_freq = midi_to_hz(midi_start, tuning);
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this.root_octave = root_octave;
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this.freqs = {};
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this.midis = {};
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this.degrees = {};
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this.octdegfreqs = {};
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this.octdegmidis = {};
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let index = 0;
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let f = null;
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for (let oct = 0; oct <= 8; oct++) {
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this.octdegfreqs[oct] = {};
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this.octdegmidis[oct] = {};
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f = get_freq(this.base_freq, scale.edivisions, scale.tonic, oct, this.root_octave);
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for (let deg = 0; deg < scale.length; deg++) {
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index = index + 1;
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this.freqs[index] = parseFloat((f * intervals.ratio(deg)).toFixed(3));
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this.midis[index] = parseFloat(hz_to_midi(f * intervals.ratio(deg), tuning).toFixed(4));
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this.degrees[index] = deg;
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this.octdegfreqs[oct][deg + 1] = this.freqs[index];
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this.octdegmidis[oct][deg + 1] = this.midis[index];
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}
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}
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this.base_freq = parseFloat(this.base_freq).toFixed(4);
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}
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base_freq() {
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return this.base_freq;
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}
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degree(index) {
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return this.degrees[index];
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}
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freq(index) {
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return this.freqs[index];
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}
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octdeg(deg) {
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const higherOcatve = deg > this.scale.length;
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const octave = this.root_octave + (higherOcatve ? Math.floor((deg - 1) / this.scale.length) : 0);
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const degree = higherOcatve ? (deg % this.scale.length === 0 ? this.scale.length : deg % this.scale.length) : deg;
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// console.log([octave, degree]);
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return [octave, degree];
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}
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octdegfreq(oct, deg) {
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if (this.octdegfreqs[oct]) {
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return this.octdegfreqs[oct][deg];
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} else {
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return null;
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}
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}
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octdegmidi(oct, deg) {
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if (this.octdegmidis[oct]) {
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return this.octdegmidis[oct][deg];
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} else {
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return null;
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}
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}
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}
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