Rare Waves - Grendel Formant Filter v2.2 coming soon. This is an unusual analog filter that modifies audio input to create vowel sounds and surreal vocal-esque tones. Updates to the original include
The ORB Formant Filter By AudioThing - Show & Reveal - YouTube
The Orb by AudioThing - Formant Filter for Mac/Windows - ADSR Sounds
Modor Formant Filter review | MusicRadar
Vocal Tract Models
Formant Filter | FREE VST PLUGINS
Illustration of the source-filter representation of vowels. The upper... | Download Scientific Diagram
How to Make a Vowel Filter in FL Studio 12 - YouTube