tonal-freq/build/index.js

Conversion between frequencies and note names

'use strict';

Object.defineProperty(exports, '__esModule', { value: true });

var tonalMidi = require('tonal-midi');

/**
 * [![npm version](https://img.shields.io/npm/v/tonal-freq.svg)](https://www.npmjs.com/package/tonal-freq)
 * [![tonal](https://img.shields.io/badge/tonal-freq-yellow.svg)](https://www.npmjs.com/browse/keyword/tonal)
 *
 * `tonal-freq` is a collection of functions to perform calculations related to frequencies.
 *
 * This is part of [tonal](https://www.npmjs.com/package/tonal) music theory library.
 *
 * ## Usage
 *
 * ```js
 * var freq = require('tonal-freq')
 * freq.toFreq('A4') // => 440
 * freq.note(440) // => 'A4'
 * freq.noteAndDetune(320) // => ['C4', 200]
 * ```
 *
 * ## Install
 *
 * [![npm install tonal-freq](https://nodei.co/npm/tonal-freq.png?mini=true)](https://npmjs.org/package/tonal-freq/)
 *
 * ## API Documentation
 *
 * @module freq
 */
// decorate a function to round the numeric result to a max
function round (m, fn) {
  m = m || m === 0 ? Math.pow(10, m) : false;
  return function (v) {
    v = fn(v);
    return v === null ? null : m ? Math.round(v * m) / m : v
  }
}

/**
 * Return the equal tempered frequency of a note.
 *
 * This function can be partially applied if note parameter is not present.
 * @function
 * @param {Float} ref - the tuning reference
 * @param {Integer} maxDecimals - (Optional) the maximum number of decimals (all by default)
 * @param {String|Pitch} note - the note to get the frequency from
 * @return {Number} the frequency
 * @example
 * eqTempFreq(444, 4, 'C3')
 * const toFreq = eqTempFreq(444, 2)
 * toFreq('A3') // => 222
 */
function eqTempFreq (ref, max, note$$1) {
  if (arguments.length > 2) return eqTempFreq(ref, max)(note$$1)
  return round(max, function (p) {
    var m = tonalMidi.toMidi(p);
    return m ? Math.pow(2, (m - 69) / 12) * ref : null
  })
}

/**
 * Get the frequency of note with 2 decimals precission using A4 440Hz tuning
 *
 * This is an alias for: `eqTempFreq(440, 2, <note>)`
 *
 * @function
 * @param {Number|String} note - the note name or midi number
 * @return {Float} the frequency in herzs
 * @example
 * freq.toFreq('A4') // => 440
 * freq.toFreq('C4') // => 261.63
 */
var toFreq = eqTempFreq(440, 2);

/**
 * Get the midi note from a frequency in equal temperament scale. You can
 * specify the number of decimals of the midi number.
 *
 * @param {Float} tuning - (Optional) the reference A4 tuning (440Hz by default)
 * @param {Number} freq - the frequency
 * @return {Number} the midi number
 */
function eqTempFreqToMidi (ref, max, freq) {
  if (arguments.length > 2) return eqTempFreqToMidi(ref, max)(freq)
  return round(max, function (freq) {
    return 12 * (Math.log(freq) - Math.log(ref)) / Math.log(2) + 69
  })
}

/**
 * Get midi number from frequency with two decimals of precission.
 *
 * This is an alisas for: `eqTempFreqToMidi(440, 2, <freq>)`
 *
 * @function
 * @param {Float} freq
 * @return {Number} midi number
 * @example
 * freq.toMidi(361) // => 59.96
 */
var toMidi$1 = eqTempFreqToMidi(440, 2);

/**
 * Get note name from frequency using an equal temperament scale with 440Hz
 * as reference
 *
 * @param {Float} freq
 * @param {Boolean} useSharps - (Optional) set to true to use sharps instead of flats
 * @return {String} note name
 * @example
 * freq.note(440) // => 'A4'
 */
function note$1 (freq, useSharps) {
  return tonalMidi.note(toMidi$1(freq), useSharps)
}

/**
 * Get difference in cents between two frequencies. The frequencies can be
 * expressed with hertzs or midi numbers or note names
 * @param {Float|Integer|String} base
 * @param {Float|Integer|String} freq
 * @return {Integer} The difference in cents
 * @example
 * import { cents } from 'tonal-freq'
 * cents('C4', 261) // => -4
 */
function cents (base, freq) {
  var b = toFreq(base) || base;
  var f = toFreq(freq) || freq;
  return Math.round(1200 * (Math.log(f / b) / Math.log(2)))
}

exports.eqTempFreq = eqTempFreq;
exports.toFreq = toFreq;
exports.eqTempFreqToMidi = eqTempFreqToMidi;
exports.toMidi = toMidi$1;
exports.note = note$1;
exports.cents = cents;