Drive

Drive is a gain control. It boosts the signal going into a stage, often the filter, until the peaks of the waveform flatten, which is called clipping. A flattened wave is richer in upper harmonics, so the sound gets denser and brighter. It gets louder too, unless the synth turns the output down to make up for it. Guitarists know the effect as overdrive, and mixing engineers call the gentle version saturation.

Rough ranges, since synths scale the knob differently:

• 10 to 30%: warmth and weight. An electric piano gets a little bark and a bass gets thicker.
• 30 to 60%: audible grit, good for leads and synth brass.
• Past 60%: plain distortion, for aggressive basses and screaming leads.

The extra harmonics help a bass on small speakers. A phone speaker can barely play a bass note’s fundamental, such as the 55 Hz of A1, but it can play the upper harmonics that drive adds, and your ear fills in the missing low note.

Where the drive sits changes the sound. Drive before the filter distorts the raw oscillators, and the filter smooths some of that new fizz away as it closes. Drive after the filter, or inside it, also clips the resonant peak, often the loudest part of the signal, so the whistle sits back and the low end sounds fuller. Manuals do not always say which kind a synth has. A quick test: turn drive up, then close the cutoff of the low-pass filter. If the grit fades as the filter closes, the drive comes before the filter; if it stays, the drive comes after it.

Drive makes a patch louder, so lower the volume as you raise it. Otherwise the louder version wins every comparison, even when it sounds worse.

In Gelato Synth, Drive is on the Filter page with Cutoff and Resonance. The filter cutoff and resonance guide and the synth bass guide both have drive settings to try.