HOWL is a simple vocoder/synthesizer. It uses formants to simulate the human voice and a pitch-space keyboard to help you find interesting melodies.


• Simple synthesizer (just a sawtooth wave nothing too complicated okay)
• Simple vocoder (four parallel bandpass filters, a bit like the Klatt engine)
• Audiobus support, so you can pipe your own audio through the vocoder and/or send the output to other software
• Adjustable pitch-space keyboard
• Cool FX (bitcrush, reverb, vibrato and tremolo)

Download it today!

HOWL is also open source (check out the code at

What’s New

Version 2.3

Fixed Audiobus support

Ratings and Reviews

4.4 out of 5
10 Ratings

10 Ratings

ludwig van beertoven ,

Fun, easy & cool

that’s not just what my business card says; it applies to howl too. this app totally fills my formant needs (which were considerable in Q2 and expected to increase for the rest of the fiscal year) and adds enough fx options to make it more than a novelty. the interface is excellent

lostproductivity ,

Very nice

Plays well with AUM and Audioshare (Audioshare being a source). Just don't forget to play (and/or lock) it while filtering and turn the knobs down a bit so you can hear your source audio coming in. Very excited to further mangle more sound experiments.

doppelganger86 ,

Amazing and completely free

This is a simple and intuitive Formant synth app that is 100% free. Virtual midi would make this a six star app. Thank you to the developer for this gift. Keep up the good work!


Daniel Clelland
14.4 MB

Requires iOS 11.0 or later. Compatible with iPhone, iPad, and iPod touch.



Age Rating
Rated 4+
© Protonome 2019


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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