The ORB Formant Filter By AudioThing - Show & Reveal - YouTube
AudioThing The Orb Formant Filter Plug-In (Download) 11-31564
The Orb - Formant Filter Plugin VST – Samplesound
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
Modor Music Formant Filter - Eurorack Module on ModularGrid
Vocal/formant filter tweaking/resources
How to Make a Vowel Filter in FL Studio 12 - YouTube