Free and quite interesting sounding too. Might have to give this one a try.
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 banks of five cascading bandpass filters, a bit like the Klatt engine)
- Adjustable pitch-space keyboard
- Cool FX (bitcrush, reverb and vibrato)
HOWL is also open source (check out the code at https://github.com/dclelland/HOWL). Send me a pull request!
HOWL is free on the app store: