# Howl: A formant synthesizer

> Formant synthesizer and vocoder with pitch-space keyboard and FX. (iPhone/iPad app by Daniel Clelland.)

- Source: https://appshunter.io/ios/app/howl-a-formant-synthesizer/id1067562312 (this page in markdown: same URL + `.md`)
- Developer: [Daniel Clelland](https://appshunter.io/developer/912177584)
- Category: Music, Entertainment
- Price: Free
- Rating: 4.30/5 from 39 App Store ratings · 36 written reviews indexed
- Age rating: 4+
- Requires: iOS 16.0 · 7 MB
- Languages: American English
- Released: 2015-12-20
- Data updated: 2026-08-12
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/howl-a-formant-synthesizer/id1067562312/reviews.md

## What is Howl?

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.

Features:

• 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 https://github.com/dclelland/HOWL).

## Key features

- Simple synthesizer (sawtooth wave)
- Simple vocoder (four parallel bandpass filters)
- Audiobus support
- Adjustable pitch-space keyboard
- FX (bitcrush, reverb, vibrato, tremolo)

## Recent user reviews (10 of 36)

All indexed reviews: https://appshunter.io/ios/app/howl-a-formant-synthesizer/id1067562312/reviews.md

### 5/5 — Nerdy fun

*2025-04-14*

This is a lot of fun to play with. It’s probably useful if you are into linguistics or phonetics. You can almost make it talk. It would be cool if consonants were added to make this fully possible.

### 2/5 — Remove audiobus with no additions come on!

*2024-08-16*

Auv3 please !!!!🙏

### 1/5 — Used to be amazing.

*2024-05-16*

iOS needs improvement. App no longer makes any sound.

### 1/5 — not working, only makes sound of microphone

*2024-02-09, version 2.3*

it doesnt make any sound and i've tried on my phone and my ipad and ive tapped on both pannels

it also makes a dot in the other panel once every 10 seconds and copied the sound of the microphone making a super high pitched buzz

### 1/5 — Broken latest version of iOS?

*2024-01-07*

Doesn't seem to do anything anymore other than try to listen to the mic and cause feedback

### 2/5 — Just feedback

*2023-02-09*

I just got this and there’s just feedback sound. Don’t know how to use it

### 2/5 — Doesn’t produce its own sound. Only uses mic.

*2023-01-16*

Self explanatory. I don’t know what happened but this used to work just fine. Not anymore

### 5/5 — Thank you for making this app

*2021-04-12*

Lots of well thought out features, this app is a thing of beauty. The world is a better please because it exists. 

It took me a bit to get used to controlling the knobs by angle. My instinct was the click the knob and hold, dragging up and down to change the value. That interface makes it easier to do fine adjustments but as is it is totally workable.

### 3/5 — Can’t save as audio file!

*2020-04-14, version 2.3*

Now don’t get me wrong, this app is well made! The only problem that I’m having is that there’s no way to save or record sound files to my phone with this app!

### 1/5 — Doesn’t do anything.

*2019-11-29, version 2.3*

It just doesn’t work.

## Frequently asked questions about Howl

### What does Howl do?

Howl is a vocoder and synthesizer application that uses formants to simulate human voices. It allows users to create melodies with a pitch-space keyboard and apply various audio effects.

### What are the key features of Howl?

Key features include a simple sawtooth wave synthesizer, a four-bandpass filter vocoder similar to the Klatt engine, Audiobus support for routing audio, an adjustable pitch-space keyboard, and effects like bitcrush, reverb, vibrato, and tremolo.

### Is Howl free to use?

Yes, Howl is a free application. There are no in-app purchases or advertisements mentioned.

### What kind of audio can I process with Howl?

You can use Howl as a standalone synthesizer or vocoder. With Audiobus support, you can also pipe your own audio through the vocoder or send the app's output to other compatible software for further processing.

### Who is Howl designed for?

This app is designed for musicians and sound designers who want to experiment with vocal synthesis, create unique vocal effects, and explore new melodic possibilities through its formant-based synthesis and pitch-space keyboard.

## Version history (last 5 releases)

### 2.4.1 — 2024-08-16

- Fixed labels in dark mode

### 2.4 — 2024-08-15

- Removed Audiobus support as it was breaking the app

### 2.3 — 2019-08-26

Fixed Audiobus support

### 2.2 — 2018-01-16

iOS 11 support

### 2.1 — 2017-01-18

This update fixes a silly bug where if you used HOWL on an iPhone with your headphones unplugged, the audio would route through the earpiece, not the speaker.

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## More apps by Daniel Clelland

- [Calx: Stack calculator](https://appshunter.io/ios/app/calx-stack-calculator/id928929230)

All apps by Daniel Clelland: https://appshunter.io/developer/912177584

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-12.*