The Gain knob doesn't change the volumeUpdated 36 minutes ago

Gain on omniGRID scales the velocity of the MIDI notes it sends. It does not turn the instrument up or down.

A drum rack often gets louder when velocity goes up, so Gain can sound like a volume knob there. Many synths, including Ableton's Drift, ignore velocity until you map it inside the instrument.

If Gain seems to do nothing, open the instrument and map velocity to its level, or to whichever control you want Gain to affect.