Pitch Mod Vs. Freq Mod?

Elektron Gear Analog Keys/Four
#1

Hi guys! Just a quick question that someone can clear up hopefully.

What’s the difference between pitch mod and freq mod in the LFO destinations. I would think that they would be the same and I can’t hear an audible difference.

Thanks!

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A4 : ENV2 cant find Osc1+2 Pitch
Exponential FM instead of linear FM in synths. Why?
#2

If you use a bipolar LFO to modulate pitch by an octave you double the freq then halve it at extremes

So a 440Hz signal modulated by an LFO will peak at 880Hz and trough at 220Hz
So it goes up 440Hz and goes down 220Hz

If you use the LFO for Freq Modulation then the frequency variation will be the same up and down (in Hz) - this offers much more useful timbral variation possibilities in practice

So one modulates pitch, the other modulates frequency

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#3

Ace.

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#4

Good to know :slight_smile:

#5

Thanks for explaining that in such an understandable way!

…and thanks @penguinpajamas for asking the question.

This forum is getting better by the day! :heart:

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#6

The Freq Mod destination is linear, making it more suitable for keeping a stable pitch when modulating in audio rate.

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#7

Add it to the manual!

3 Likes
#8

haha … yeah definitly a big thank you for asking and answering the question!
i was also wondering

#9

So freq mod = linear FM
pitch mod = exponential FM
?

simples if so

#10

I suppose in my ignorance I simply don’t understand the difference between pitch and frequency, as I always thought pitch was simply the result of increased frequency.

#11

This has more to do with FM synthesis terminology than pitch though, at least that is how I see it.

#12

Right, as I say it’s just my ignorance. But I am still stuck at:

“One modulates pitch, the other modulates frequency”

As I can’t see how you would modulate pitch, other than by modulating frequency, and vice-versa.

Just need to do more reading.

#13

think of modulating semitones then , it’s just a way to anticipate which one is exponential (wrt Hz)

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#14

umm, no wait, I thought the diff between linear and exponential FM is that linear FM does not destabilize tuning when FM is applied? Whereas exponential FM always changes the perceived pitch when FM is applied?

Most FM synths do linear FM because of this pitch stability, exponential FM is not really good for ballads as its almost never in tune

#15

I watched a good Youtube video on the difference between the two once and understood it superbly for the precise length of the video, then it was gone.

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#16

If I understood correctly:

The paradox and at the same time the key to understanding the matter is that 1V/oct is called exponential.

From that it follows, that if you have a modulator with a range of +1V to -1V:

With EXP FM (pitch mod) you modulate the pitch one octave up to one octave down–> symetrically
With LIN FM (freq mod) you modulate the pitch up half the amount relative to the downward modulation --> asymetrically

Therefore you could say that with Pitch mod you indeed modulate in semitones (EQUAL AMOUNT UP AND DOWN)
and with frequency mod you modulate the number of Hz (remember that for an octave up you need to double the frequency, and for an octave down you need to halve it). This means that the “upward modulation” is less than the “downward modulation” if you measure in semitones.

As to why that asymentric modulation is seen as more musical; that is a mystery to me though…

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#17

Ahh I get it. Remember, the well-tempered western tuning system is not based on the harmonic cycle. So modulating with an lfo scaled in semitones is not going to easily get you those nice consonant fm sounds.