Like the Vocal Animator, this is a filter bank tuned to the formant frequencies of typical singing voices. Unlike Growler, however, the filters do not animate on their own - instead they are set up to generate specific singing sounds. The filters are preset to frequencies, bandwidths, and gains that are taken from measurements of human singers.
One of the easiest ways to get a good sound from Formants is to use it like a regular VCF. For example, control Fc with an ADSR. Then put a second modulation source into the vowel CV - something as simple as a slow LFO will add interest.
Use it as a filter bank. Just set the knobs for a good sound and leave it fixed to add vocal tones to a pad. Again, modulating the vowel CV can easily give great results.
Try to synthesize something like singing by sequencing the vowel CV of several formants. Leave the Fc in place, or move it slightly as the input pitches move.
The LEDs across the top indicate which formant is currently being “sung”.