Used to add additional gain to the signal path and particularly useful for boosting level after overzealous use of the High-pass Filter. It’s also worth noting that with the Low-pass Filter open, or partially open, increasing the VCA Gain can cause a sound to sustain continuously.
As explained in the Filters (VCF & HPF) section, Oddity3 has two envelope generators either of which can be assigned to the VCF or VCA. Here we select one for the VCA and use the red slider to adjust the amount.