Envelope in Retrologue Filter Section

I’m learning Retrologue 2. The documentation says that the Envelope control in the filter section…
"Adjusts the cutoff modulation of the filter envelope. Negative values invert the modulation direction."

What does “cutoff modulation” mean? ( I know what a ‘cutoff frequency’ is and there are lots of controls that affect that. ) But what is ‘cutoff modulation’ and what does it mean to invert its “direction”?

And while we’re about it, what about the Cutoff and Resonance Controls? The documentations says

Cutoff Controls the cutoff frequency of the filter.

It’s marked off in Hertz but some filters, such as bandpass filters have two cutoff frequencies. What does cutoff control in that case?

Resonance Emphasizes the frequencies around the cutoff. At higher settings, the filter self-oscillates, which results in a ringing tone.

“Emphasize”, meaning what, exactly? Also same question WRT bandpass filters.

Thanks in advance.

What does “cutoff modulation” mean? ( I know what a ‘cutoff frequency’ is and there are lots of controls that affect that. ) But what is ‘cutoff modulation’ and what does it mean to invert its “direction”?

In synthesis, “modulation” usually refers to a temporary, dynamic change to a parameter. In this case, cutoff modulation simply refers to the fact that the filter envelope will change the cutoff frequency over time, based on your settings.

The Envelope knob adjusts how sensitive the cutoff frequency will be to modulation coming from the envelope. A setting of 100% means that the cutoff frequency will reach its maximum value (22000Hz) before decaying to the sustain level. Setting the envelope to less than 100% prevents the filter from “opening” as much before decay. Negative values invert the behavior of the whole envelope. For example, if you’re using a low pass filter and set the Envelope to -100%, instead of decaying from 22000Hz to your sustain level, the filter will “rise” from 10Hz to your sustain level instead.

The sustain level must be set to a value lower than 100% for the decay to have any effect. 0% sustain will always return the filter to your set cutoff value, regardless of the value of the Envelope knob.

And while we’re about it, what about the Cutoff and Resonance Controls? The documentations says
Cutoff Controls the cutoff frequency of the filter.
It’s marked off in Hertz but some filters, such as bandpass filters have two cutoff frequencies. What does cutoff control in that case?

For most filters, the cutoff frequency is the point where the signal level has been reduced by -3db, where the effects of the filter start becoming highly audible. Increasing the resonance “empathizes” this -3db point, or in other words makes it louder, just like using a peaking equalizer. A low resonance slightly boosts a range of frequencies around this cutoff point, while a high resonance boosts a narrower frequency range at a much higher level.

For bandpass filters, the cutoff frequency is instead the exact center of the two filters, where the signal is completely unmodified. Resonance here primarily boosts the level of the unmodified signal.

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Thank you!! This was very thorough and helpful. (Why can’t the Steinberg’s User Manual go into this much detail?)