Filter cutoff pitch modulation

Hello, my friends

I've doing some tutorials and I have this doubt: What exactly is cutoff pitch modulation?

The modules and macros manual says (2-pole FM filter):

The cutoff frequency is determined in the logarithmic scale at the "P" (cutoff pitch) input port and can be modulated in the linear frequency scale using the "F" (cutoff frequency) input port.

I know what is a modulation but I find it difficult to understand it in this context.

Sorry for these basic questions, but... you know, every expert was a beginner once.

Thank you

 

It seems to be a difficult question.

Ok, let me put this in another way...

If I have a filter with a pitch cutoff and I modulate the cutoff frequency (ex, in a 2-pole filter FM)... As far as I'm understanding the cutoff frequency, in this case, it's not the frequency at which the filter works but rather the frequency at which it works during a certain period of time:

Ex...LP filter with a pitch cutoff of, let's say 69 (in Reaktor the range is 0~127 and 69=A3=440 Hz). So, anything above 440 Hz is constantly filtered.

But if I apply a frequency modulation of 40 Hz, for ex, I'm telling the filter to cut everything above 440 Hz, 40 times per second.

Am I thinking correctly?

 

no you are wrong: the frequency-input can be used for frequency-modulation and pitch modulation:

The pitch input is an event input (red) so it is normally used for midi pitch event or slow sources like LFO or ADSR in sum.
The frequency-input is an audio input (black). So you can use event sources and audio sources (feedback!).
In the attachment you see two simple examples:
- yellow: the LFO has an amplitude of 1. So if you have a midipitch 69 (means 440Hz) the cutoff frequency is at 440Hz. The LFO would change the cutoff to a range of [439Hz .. 441Hz] which you don't hear. If you have a midi pitch three octaves lower (pitch = 33 means 55Hz) you have a range of [54Hz .. 56Hz] and you would hear modulation of filtered source f.i. saw wave.
So with yellow solution you get different sound modulation for lower and higher sounds. If you want a more concise solution you have to multiply with a factor [0 .. 500]. You see the „problem”? different filtering for different source-frequencies
- blue: if you want a modulation in the same way for lower and higher sounds you can use a simple calculation from pitch to frequency: LFO range is [-1 .. +1] so with an inserted p2f-module you have a modulation of 1 halftone. Midi pitch 69 would change to [68 .. 70] and midi pitch 33 to [32 .. 34].
Add a multiplier to get different sound modulation.

Both modulations are usefull.

ciao herw

 

herw, Thanks for taking your time to explain it with such a good example. I understood it. I'm trying to understand how modulation can be applied (and its results) in different contextes (pitch modulation, frequency modulation, envelopes, etc, etc). I think more doubts will come with time.

Thanks again