Classic oscillator pitch mod. with an LFO?

May 6, 2009 at 7:51pm

Classic oscillator pitch mod. with an LFO?

Hi most excellent list,

I’m trying to build a ring mod based on the moogerfooger pedal. I would like to change the frequency of the modulation oscillator with an LFO (which is based on another oscillator)- classic analog style oscillator pitch modulation with an LFO.

Getting ring modulation is easy with a [*~] and an oscillator multiplying the input. Also, I was able to modulate the freq of the modulator by adding [+~] the LFO as in the FM tutorial (8?) example but I’m not getting the same behavior as the LFO section on the moog pedal.

What I’d like to do is at 100% depth setting of the LFO that it would sweep the mod freq from 0hz to whatever its set at or for example if the depth was set at 50% that and that mod freq was 100hz the LFO would sweep the carrier from approximately 25hz to 75hz. In the FM patch the both the high and low range of the carrier gets pushed downward and upward as the depth increases so if I want the LFO sweep to start around zero the mod freq goes higher then its initial setting setting. I guess there must be a pretty simple solution but I’m missing it. I did try LFOing the mod’s floating freq input in the control realm with a sig~ and some math to make it unipolar but I could hear a lot of zippering as it swept so I’d like to do this in the audio realm if possible especially now having built a nice new killer LFOs in MSP based on Gregory Taylor’s excellent tutorials.

Thanks in advance. Sorry if this was a little meandering.

Best,

Bradford

#43700
May 6, 2009 at 11:24pm


when you create it, it is 0. – 1. , right?

so first -1, then multiply, an then [- ] should do it.

-110

#156933
May 6, 2009 at 11:46pm

thanks…. but I’m not understanding you
could you or someone else elaborate or give a small example?
best
B

#156934
May 7, 2009 at 12:06am

I think it would help to read up on what low frequency oscillation, carrier, and modulating waves are:

http://en.wikipedia.org/wiki/Low_Frequency_Oscillation

#156935
May 7, 2009 at 12:18am

Did it seem from my question that I don’t understand what I’m talking about? If so please let me know what you think I’m misunderstanding? I’ve made this patch in other software (bidule) and my nord that’s structured more like a traditional modular synth. I’m having a hard time doing it with max and need a tip or two.

thanks
B

#156936
May 7, 2009 at 6:14am

sorry I got carrier and modulator backward in my original post- I fixed it but I’m still confused

#156937
May 7, 2009 at 7:05am

The output of a cycle is in de range [-1 1]. Adding 1 to this output (+~ 1) creates the range [0 2]. Multiplying this with half the range you want e.g. 50 (*~ 25) will create an output range [0 50]. Is that what you meant?

_
johan

#156938
May 7, 2009 at 6:06pm

Yay… duh. I figured it out. Thanks again
If anyone following this is confused about the solution let me now and I’ll post an example when I get a chance.

best

b

#156939

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