One-Knob Filter is a multi-type filter used for plugin design. Type: Selects the type of filter. Frequency: Sets the center frequency for emphasis or attenuation. Q/Order: Adjusts the width/order of the affected frequency range. Does NOT have any effect with the Low Shelf and High Shelf types. Gain: Controls the overall amplitude or level of the filtered frequencies. Does NOT have any effect with the Low Pass and High Pass filters.