Formant

A formant is a boosted region in a spectrum that stays at roughly the same frequencies regardless of the pitch being played — the resonant fingerprints that make vowels recognizable.

Vocal-style wavetables work by moving formant peaks across frames while the fundamental holds still, which is why scanning them feels like a mouth opening and closing. Because formants live in the pattern of partials rather than in the time-domain shape, formant motion is far cleaner when done per-partial, as spectral morphs do, than by crossfading raw frames.