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Variable rate controllable audio pitch shifter


A variable speed pitch shifter written in JavaScript.

Here is a demo you can try in your browser!


Here is a simplified psuedo-example:

//Create a pitch shifting object 
var shifter = require("pitch-shift")(
  function onData(frame) {
    //Play / write out frame.  Called whenver data is ready 
  function onTune(t, pitch) {
    console.log("Got pitch ", pitch, " at time ", t)
    //This is the amount to scale the sample by 
    return 1.0
//Feed some data to the shifter 
shifter(new Float32Array([1, 1, 0, 1, 0, 0, 0 /* ... etc */ ]))

For a more complete working example, check out test/test.js or example/index.js


npm install pitch-shift

require("pitch-shift")(onData, onTune, options)

Creates a pitch shifting function

  • onData(frame) Called when a pitch shifted frame is ready.

  • onTune(t, pitch) Called when a frame of audio needs to be processed.

  • options An object full of options to pass to the pitch shifter

    • frameSize size of frame to process (default 2048)
    • hopSize the distance between frames in samples. Must divide frame size. (default frameSize/4)
    • dataSize maximal allowable size of a data frame (default frame_size)
    • sampleRate Conversion factor from samples to seconds. (default 44100)
    • analysiWindow analysis window. must be a typed array with length equl to frame size (defaults to Hann window)
    • synthesisWindow synthesis window. must be a typed array with length equal to frame size (defaults to Hann window)
    • threshold peak detection threshold. Set to 1.0 to always take maximum, otherwise set lower to detect half tones. (default 0.9)
    • minPeriod Minimal resolvable period. (default sampleRate/400)

Returns A function that you call with a frame of data.


(c) 2013 Mikola Lysenko. MIT License

Gettysburg adress reading by Britton Rea. Recording obtained from the Internet archive.