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 Forum index » Clavia Nord Modular » Nord Modular G2 Discussion
How to get a natural analog sound from oscillators
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mosc
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Joined: Jan 31, 2003
Posts: 17563
Location: Allentown, PA
Audio files: 123
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PostPosted: Sun Feb 06, 2005 10:26 am    Post subject: How to get a natural analog sound from oscillators Reply with quote  Mark this post and the followings unread

This converstation is being imported fromt the Nord Modular mailing list. I thought it was of interest and should be preserved here:


I was wondering how you all deal with a "problem" that has been
troubling me since I got my G2 rack last spring. Say I am working on
a patch, specifically one with sequencer modules (which is what i was
just working on when I encountered the problem). I have the seqs
running, and in the meantime am adding more modules (osc or control
seqs, etc.). Obviously, the G2 has to recalculate how it will use the
load with the new modules, etc. but when it finishes and the sound
starts again, it sounds completely different! This issue woulnd't be
so frustrating except that things NEVER sound the same after adding or
deleting modules.

I apologize in advance if this question has been asked before, but I'm
till a n00b at this stuff. Thanks for any help and/or reponses!

-Mariana


The basic idea of 'virtual analog' is to not always have exactly repeating
sounds, just like samples that will simply always sound exactly the same.
Instead, the idea is to get roughly the same sound, but with the slight
changes from note to note that characterize acoustic instruments and analog
synths. To do this in a convincing way is quite an art, an art that each of
us has to learn over time.

This issue you mention has in general to do with how digital oscillators
have a defined pitch but an undefined phase. Small shifts in phase between
the waveforms of two or more oscillators can produce drastic changes in
timbre. This is in fact one of the hallmarks of analog synths, they do never
sound the same as well. Samples however will always sound the same, too much
the same in general.

What one needs to keep in mind is the difference between digital and analog
oscillators. Analog oscillators always drift constantly, so the phase
relation between two or more oscillators is constantly changing, creating a
chorus effect. Digital oscillators do not drift by themselves, so when using
more than one oscillator they should always be detuned slightly by two to
ten cents. This will recreate that lush and lively drifting effect of analog
oscillators. But if the digital oscillators are not slightly detuned, every
voice will appear to have a different timbre and after every recalculation
of the patch the timbres for each voice will change. This is simply because
the phase relation stays fixed during the sounding of a note if the digital
oscillators are not purposely detuned.

The only way to prevent oscillators to have undefined phase shifts is to use
hardsync, meaning that the output of the lowest tuned oscillator is
connected to the sync input of oscillators tuned to a higher pitch. But this
will also give the typical sonic effect of hardsync, and might not be what
one wants.

So, the rule is to always slightly detune the second and third oscillators
in a voice, or else use hardsync.

A good trick to mimic the ever and randomly driftting analog oscillators is
to feed them all a slowly varying smooth random LFO signal to their pitch
modulation inputs and open the modulation knob just one tick. Of course each
oscillator must have its own randomly tuned random LFO waveform. This will
give different sounds on each keypress and also after each recalculation of
the patch. But it will be a dynamic and natural effect, immediately giving
life to the sound.

Hopefully this gives you a bit more insight in the matter.

/Rob



In addition to my previous reply a simple two oscillator patch that shows
this detuning thingy. Both oscillators have a clocked Rnd module connected
to their pitch inputs. These Rnd modules are clocked by the oscillators
themselves, so each period of the waveform of an osc is slightly different.
If you mute the two Rnd modules the static character of the oscs can be
clearly heard. But if both Rnd modules are On the sounds get very lively.

Mostly lower notes need a little deeper modulation as higher notes. This is
done by applying the Keyboard morph on the pitch inputs of the oscillators.

/Rob



And in adition to what Rob said... It also helps to trigger the rst inputs of oscilators with they keyboard gate signal...
than you dont have to use hardsync

Sven




Quoting Sven Roehrig:


> And in adition to what Rob said... It also helps to trigger the rst
> inputs of oscilators with they keyboard gate signal...
> than you dont have to use hardsync


This is a usefull tip but beware ... it might give clicks when a voice is
re-used, depending on your envelope/polyphony settings/requests.

For sequenced patches this probably is not a problem.

Jan.

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Parametex



Joined: Feb 07, 2005
Posts: 9

G2 patch files: 1

PostPosted: Mon Feb 07, 2005 3:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Mariana and Rob,

I have encoountered a very similar problem described by Mariana. This problem however does not have anything to do reseting the oscillators and it does not manifest nitself as a small variation but a major change of sound. The problem is that when I pick up a new module and the recalculation occurs the G2 (1.24) resets the position of controller potentiometers. I have not quite succeeded to narrow down the exact bug, but basicly the synth resets the positions of pots under external midi controll and it possibly has something to do with the morph group associations also. Anyhow dragging a new module to the batch becomes a drag.

Peace,
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Tusker



Joined: Feb 03, 2005
Posts: 110
Location: Texas

PostPosted: Mon Feb 07, 2005 5:05 am    Post subject: Reply with quote  Mark this post and the followings unread

I tried Rob's tip on modulating the oscillators with clocked random step generators on G1. I had independant oscillators each clocking their own step generators. I found my sweet spot for modulation depth to be 1 in the high ranges and about 10 in the lower ranges ... using the keyboard morph Rob recommended. My basic minimoog patch became a lot more playable and smooth sounding throughout it's range. Even the downstream waveshaping effects (overdrive, clip) seem to have become more musical. Wow.

The only thing that I can't figure out is how to explain two aspects of this trick. When I raise the modulation depth to extreme levels, I hear a low frequency burping. How does this happen if the oscillators are clocking the step generators at audio rates? Secondly, it seems counter intuitive to create a smoothing effect through the use of a step function...?

Just curious. Thanks for making my G1 a new synth! Laughing

Jerry
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Rob



Joined: Mar 29, 2004
Posts: 578
Location: The Hague/Netherlands/EC
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PostPosted: Mon Feb 07, 2005 2:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

The mentioned patch

/Rob


DetuneExample.pch2
 Description:
Example of random detuning of oscs to increase liveliness

Download
 Filename:  DetuneExample.pch2
 Filesize:  1.55 KB
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