AudioStretch for iOS

AudioStretch lets you change the playback speed of audio files without changing the pitch and/or change the pitch without changing the speed. Handy for learning music by ear, transcription, or just listening to your music library in a new way.

Unlike most time stretching apps, AudioStretch allows you to reduce the speed to zero, so you can “freeze” notes or chords. You can even hear the sound as you touch and drag the waveform.

Features include:

  • Simple uncluttered user interface
  • Wide range of playback speeds: -250% to +250%
  • Shift pitch by up to 12 semitones up or down
  • Freeze notes or chords with 0% play speed
  • Hear the sound as you drag the waveform
  • Overview display for instant seeking anywhere in a track
  • Super-easy single-button looping feature
  • Use any song in your iPhone’s music library (*)
  • Supports iOS 5.1 and up (iOS 6 recommended)

A one-time $2.99 (or equivalent) in-app purchase is required to play beyond 2 minutes. Other than that, it’s 100% free.  (In-app purchase not required for early adopters, that is anyone who first installed before 4 Jan 2013.  If you’re an early adopter, but you are getting the two-minute limit, contact

[Update: As of late Feb 2013, I changed the pricing model for AudioStretch. It’s no longer a free download with in-app purchase to remove the 2-minute limit. Instead it’s a pay-to-install app (with no subsequent in-app purchase).  I might create a free “Lite” version at some point; in the meantime, if you’d like to get an idea how the app behaves, try the Flash version of AudioStretch.  It looks just like the app running on an iPhone, and has much the same behavior.  The real iOS version runs more smoothly and has a bunch of additional features – keyboard/spectrum display, support for many more audio file types, optional audio modes (left mono, right mono, left-minus-right aka vocal suppress) -Gerry 30 April 2013].

(*) Other than very old iTunes purchases that are protected with FairPlay DRM. In iOS 5, songs in mp3 format (or anything other than aac/m4a) load very slowly. Files beyond 1 hour in length will be truncated.


Click the “Songs” button at the top-left to choose a song from your iPod Music Library. (If you don’t have any music on your iPhone, you can add music from your PC or Mac using the iTunes application, or buy music through the Store in the Music app on your iPhone).

After selecting a song, the song name, artist, and album will appear in the title bar, and a waveform of the first few seconds of the song will appear. (If no waveform appears, it’s because the song starts very softly).

Click the Play button to start playing.  Click it again to Pause playback. Click the Rewind/Fast-Forward buttons to move backwards/forwards rapidly through the song. Alternatively, you can simply drag or ‘flick’ the waveform.

Adjust the Speed (% of normal speed) and Pitch shift (semitones) of the playback by clicking the corresponding stepper controls.

To loop a portion of the song, first click the Loop button to set the loop start time. The letter ‘A’ will light up beside the Loop button, and the ‘A’ loop start marker will appear on the waveform display.  Click the Loop button a second time to set the loop end time.  The letter ‘B’ will light up beside the Loop button, and the ‘B’ loop end marker will appear on the waveform. Clicking again clears the loop.

Known issues

  • As of version 1.2, iOS 5.1 is supported, but only aac/m4a files will load quickly; other formats, for example mp3, will load a bit slowly.  It’s only an issue in iOS 5.1. In iOS 6, mp3s load just as fast as aac.
  • Some early adopters got hit with the two-minute limit.  I set things up such that anyone updating from the previous version (1.3, released 13 Dec 2012) will not have the two-minute limit – provided they’d run version 1.3 at least once.  For technical reasons, I can’t programmatically detect whether someone has run a version earlier than 1.3, and unfortunately some early adopters didn’t update to and run version 1.3. If you’re one of them, and you’d like to continue using the app without the time limit but really cannot or don’t want to spend $2.99, just write to me at, and I’ll send you instructions for removing the time limit.


To report bugs and/or request features, feel free to send email to or add a comment below.


11 Responses to AudioStretch for iOS

  1. Matt says:

    I had the previous version of this app (1.3) and all was fine. Since the update I can’t go past the two minute mark.

    • Playing beyond two minutes now requires an in-app purchase (initially just $0.99, just a token amount really, and the smallest price I can set). It’s only meant to apply to new users. If you’d installed and run the previous version, you should not have had the two-minute limit. Is it possible you updated to 1.3 a few weeks ago, but didn’t run it?

  2. Jennifer says:

    I have used this app many times but when I upgraded and opened I have a 2 minute time limit. Please help. Thank you!

  3. Sorgon says:

    this is very misleading when you go to the app store and it’s actually $3.99 even to try it.

  4. David says:

    Can u lower a song then save it to your iTunes library?

    • Hi David, AudioStretch provides a wide range of export options – email; saving to various cloud services (Dropbox, iCloud, OneDrive, etc.) via Apple’s Document Picker API; and transfer via the “Open In…” mechanism to any app that supports it. Unfortunately it cannot export to the iTunes Music Library, and as far as I can tell, no app can do that. What you can do, however, is use one of the other export methods to get the file to your PC or Mac, and add it to your iTunes library there; you can then sync that to your iOS device’s iTunes Music library.

  5. Roberto Soggetti says:

    beautiful and useful app… it really works well. One thing I’d like to see in a future release is the ability to select a darker gui for using the app at night, all that white is dazzling.

  6. Dave hall says:

    I really love this app but it wont find songs i download from iTunes Store direct to iPad. iPad says the song is stored on type iPad but AudioStretch doesn’t see it. Frustrating

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