Real-time control knob - cutoff

[jcw]

Hi,
Would someone be able to tell me what parameters affect the real-time control knob for cutoff. For example with a piano the knob has not much affect, but with a fast synth sound it does. I have looked through the program pages to try and find a parameter that controls how the knob works without success.

I have searched through the op. guide and parameters, but can’t find anything that helps. It will be something straight forward....I am probably searching for wrong term.

Thanks in advance
John