Hey there!
What are the units for filter frequency and resonance? If I have a specific target frequency in Hz and resonance lift in dB, what 0-1 settings should I set in a modulation device? What about Drive?
I found the modulation filters follow the same curve as the native track-fx “Digital Filter” device. There is a Formula Device preset called “Keytracker Cutoff”, it will actually map digital filter to a keytracker. Also there this older work from me: [Effect Presets] tuned keytracked effects formulas/doofers Ktrk 1.1 - with more presets for other devices, but not modulation.
You can actually use the formula device to control a modulation macro and keytrack tune the instrument filter with the “Digital Filter” preset. I tried, it works, tuned bassdrum through high resonance with some drive - instant subbass.
As for the resonance and drive I can only say it’s different between the filters, it depends on their algorithm. For example the K35 Filter needs stronger push in resonance, while the Moog Filter rings much more easily, and the Diode Filter is somewhere in between and has a nonlinear reso range. The drive probably just boosts the signal, and sounds pretty similar between the effects, but I’ve not yet measured anything with that, it’s enough for me to tune the filters to a specific frequency. I.e. you can use the formula device to write a frequency to the filter (i.e. use a formula like y = frq2flt(440.0) to tune your filter to that frequency…