Freelizer

Simple package on pure JavaScript with Audio Web API usage that was made for purpose of calculating sound frequency from microphone.

Live example of usage

Some important information

Has been tested only in desktop and mobile Google Chrome version 87.0. Package doesn't include polyfills. Stable work in other browsers isn't guaranteed. Requires support of Web Audio API. Has 0 dependencies from other packages.

Data that library provides

1. Frequency of sound from microphone.
2. Nearest note letter that nearest to sound frequency.
3. Frequency of nearest note.
4. Octave number of nearest note.
5. Deviation between frequency of sound from microphone and frequency of nearest note.

Usage example

import { freelizer } from 'freelizer'

;(async function () {
    try {
      const { start, subscribe } = await freelizer()
      start()
      subscribe(console.log)
    } catch (error) {
      // Error handling goes here
    }
})()

A little explanation for usage example

Import freelizer function

import { freelizer } from 'freelizer'

Call freelizer function. Beware, that freelizer is asynchronous. It returns an object that contains functions. Call of freelizer asks for permission of using microphone.

const { start, subscribe } = await freelizer()

Use start() function to launch process of sound listening.

start()

Use subscribe() function that takes callback-function as argument. Callback-function will get data object as parameter. Callback will be called on each animation frame.

subscribe(console.log)

Example of console output:

{
  frequency: 163.71831025615992,
  note: "E",
  noteFrequency: 164.81377845643485,
  octave: 3,
  deviation: -1.0954682002749223,
}

freelizer

Asynchronous function that call returns an object that contains functions for library mainpulation. These functions are:

• start()
• stop()
• subscribe()
• unsubscribe()

Calling example:

const { start, stop, subscribe, unsubscribe } = await freelizer()

Error handling

Since the function is asynchronous it recommended to use try/catch statement. The most frequent cause of errors is situation when user blocks microphone usage.

try {
  const { start, subscribe } = await freelizer()
} catch (error) {
  // Error handling goes here
}

start

Function that launch process of sound listening. During this process all functions-subscribers are called on each animation frame.

stop

The opposite of start function. It stops process of sound listening.

subscribe

Provides mechanism of subscription to sound listening stream. It takes callback-function as argument. Callback-function will get data object as parameter. Callback will be called on each animation frame.

Usage

const callbackExample = data => console.log(data)
subscribe(callbackExample)

Callback-function argument

Callback-function takes object that contains the following fileds:

• frequency: Float Number
• note: String
• noteFrequency: Float Number
• octave: Integer Number
• deviation: Float Number

{
  frequency: 163.71831025615992,
  note: "E",
  noteFrequency: 164.81377845643485,
  octave: 3,
  deviation: -1.0954682002749223,
}

Its possible to subscribe as many functions as needed.

unsubscribe

Unsubscribes callback-function from listening of stream. Takes callback-function that previously was transmitted to subscribe function. Remember that it doesn't work with annonymous functions.

Usage

Example that logs data in console for 5 seconds:

const { start, stop, subscribe, unsubscribe } = await freelizer()
start()
const callbackExample = (data) => console.log(data)
subscribe(callbackExample)
setTimeout(() => unsubscribe(callbackExample), 5000)

Sources

ACF2+ algorithm

Original algorithm that returns frequency value from waveform was taken from "Simple pitch detection" repository.

Theory of music

• "Equations for the Frequency Table"
• "Musical Note Frequency Calculator"
• "guitardialogues"