If you increase the filter Resonance parameter to higher values, the filter begins to internally feed back and, as a consequence, begins to self-oscillate. This results in a sine oscillation—a sine wave—that is audible.
To start this type of oscillation, the filter requires a trigger. In an analog synthesizer, this trigger can be the noise floor or the oscillator output. In the digital domain of the ES2, noise is all but eliminated. Therefore, when the oscillators are muted there is no input signal routed to the filter. Turn on Filter Reset to provide a trigger signal that can be used to drive the filter to self-oscillate.
Click the Filter Reset button to turn on.
When this button is engaged, each note starts with a trigger that makes the filter resonate/self-oscillate immediately.
Click to turn on the Fat(ness) button—below the other filter slope buttons.
An increase of the resonance value results in a rejection of bass—low frequency energy—when using lowpass filters. Use the Fatness button to compensate for this side effect and to obtain a richer sound.