Currently in vital, when FM’ing one oscillator into another, when unison is enabled, the modulator is computed in full, including all the unison voices being summed, and used “as a whole” by the carrier input.
As you can see in the following video: Synthesizing Cymbals With Serum in Serum the unison voices are all considered separately, so that the modulator/carrier relationship is by pairs of unison voices, rather than the summed signals, or at least, it sure sounds like some variation of that (since clearly for differing unison voices for the modulator/carrier, something else must be happening).
It’s quite clear when trying to mimic this in Vital that the sound is severely lacking.
Being able to directly create more metallic timbres like this would be amazing.
Adding an extra FM mode to support this would be fantastic.