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Synthesis 101 question
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Synthesis 101 question
Addled
So, I'm about to embark on building the chopping kinky kit that just arrived today. (Super stoked to pair this up with my 4me smr by the way.) And I got to thinking wave folding is additive synthesis yes? Correct me if I'm wrong, please! Up until now I've been mainly doing what I think is subtractive, vcf filtering a vco source. And it occurred to me I know some terms whose definition I'm not familiar with. Long story short, what are the basic approaches to synthesis. From what I've been able to pick up so far it seems like there's at least the following:

Subtractive
additive
Fm
Wavetable
Granular

Is this too far off? Are there types I'm missing? Where does digital fit into this? I can Google and search the specifics on my own unless you care to take the time to educate me. Mainly I just want to know what to research and how to categorize things in my head. Thanks in advance!
Dcramer
Well.... hmmm.....

The trouble with the term ‘Additive Synthesis’ is that it’s easy to interpret any technique that builds up complex sounds from simple ones as additive.
Yes, wavefolding adds harmonics to a simple waveform but it’s really more of a ‘Time Domain’ distortion or waveshaping technique.
I tend to think of Additive as being in the Frequency Domain.
Usually we see Additive implemented in software, a realm where it’s easy to handle all the data needed to control hundreds of sine waves and their envelopes.
Since you’ve got an SMR, you may be interested to see that I posted a technique for using it as an Additive oscillator, albeit with a mere six sine waves. thumbs up
Addled
Ok. I think I grok what you're saying about 'Time domain' distortion. It's kind of clipping and you're just changing what's existing in the original waveform not adding from an external source. Is that the general idea?

Edit: I'll check out your patch. It seems like I'll never reach the bottom of that SMR, I'm dedicating a lot of hp real estate into support modules for it and enjoying the results.
Dave Peck
The term "additive synthesis" refers to making a complex waveform by adding multiple sine waves together at different frequencies and various amplitudes - essentially creating the waveform from it's individual harmonics.

A wave folder is a type of waveshaper. It can make a simpler waveform more complex and can increase the harmonic content of the signal, but it is generally not considered additive synthesis.
cptnal
Add "phase modulation" to your list, à la Casio CZ-101 and friends. Implemented in the WMD PDO (amongst others, I assume) and doable in Shapeshifter (if I understand it right).

Be sure to check out the SMR patches thread, if only to see the one I recently posted. Mr. Green
https://www.muffwiggler.com/forum/viewtopic.php?t=180688&start=81

It's a strange fish. You have to lavish attention on it, but it will reward you many-fold. This is fun!
Dr. Sketch-n-Etch
Additive synthesis is the creation of sound by adding harmonics. It requires the summing of many carefully tuned sine waves and is generally only done digitally because analog circuitry isn't precise enough and would be very complicated.

Subtractive synthesis is the creation of sound by filtering harmonics out of simple waveforms rich in harmonic content (such as sawtooth or square waves). This is the normal mode of synthesis.

Wavefolding is neither additive nor subtractive synthesis. It is really more a form of distortion.
ndkent
For decades additive synthesis has meant creating a sound by generating a number of harmonically related sine waves that when mixed together create a more complex waveform.

Recently in a fairly understandable sort of one or the other classification push some people started using the logic that because wavefolding can produce what might be considered an opposite effect of a filter, adding harmonics to an existing wave, it must therefore be Additive Synthesis. A proper implementation of additive synthesis lets the user control the amplitudes of the many sine waves over time.

The problem is that wavefolding is not at all similar to the long accepted technique of additive synthesis, what it relates to is waveshaping, part of the process of generating the waveshapes that a synthesis method is typically then used on, though it doesn't exclusively need to be used as a first step in the signal path.

While it does indeed generate frequencies not in the original wave, one does not get to determine which ones as specifically though one can dynamically control the wavefolding

Besides that confusion over long time use of the term, I'll add that in some classic more complex wavefolding circuits one can in fact remove harmonics, not just add some. Though as with all waveshaping, that depends on the initial waveform, if one can turn a saw to a sine (removing harmonics), the same waveshaper will not turn a square to sine.

As for the list of methods of synthesis, as I see it, the most popular methods provide a wide and flexible method to create a lot of sounds. One can keep going and list a lot more methods that create a novel range of sounds in a more limited range.

Also modeling synthesis, not on your list, is an umbrella that holds an infinite number of processes conceived or unconceived that replicate a process that generates sound waves.
dubonaire
double post
dubonaire
Dr. Sketch-n-Etch wrote:
Additive synthesis is the creation of sound by adding harmonics. It requires the summing of many carefully tuned sine waves and is generally only done digitally because analog circuitry isn't precise enough and would be very complicated.

Subtractive synthesis is the creation of sound by filtering harmonics out of simple waveforms rich in harmonic content (such as sawtooth or square waves). This is the normal mode of synthesis.

Wavefolding is neither additive nor subtractive synthesis. It is really more a form of distortion.


This is the most concise response, by a man who has designed one of the most precise analogue sines in the game.
Addled
Thanks folks! I see the distinction between wave folding and additive now. Also, for my homework I need to add phase modulation and physical modelling to my list of types which gets the list to this point:

Subtractive
Additive (Primarily a digital approach)
Fm
Wavetable
Granular
Physical Modelling
Phase Modulation

I'm mainly just trying to grasp the common approaches to synthesis as this point.

cptnal wrote:
Be sure to check out the SMR patches thread, if only to see the one I recently posted. Mr. Green
https://www.muffwiggler.com/forum/viewtopic.php?t=180688&start=81

It's a strange fish. You have to lavish attention on it, but it will reward you many-fold. This is fun!


Damn, that's great. I don't have a stages in my rack, but I'll have to read your notes when I'm more sufficiently caffeinated to see if it's something I can approximate.
Gizmo
Dr. Sketch-n-Etch wrote:
Additive synthesis is the creation of sound by adding harmonics. It requires the summing of many carefully tuned sine waves

It's important to respect this definition and "hold the line" against alternatives if it is to remain at all useful. Additive synthesis is necessarily "built up" from simpler components. Hammond drawbars are specific examples of the method. Conventional pipe organ stops as well.

ndkent wrote:
Also modeling synthesis, not on your list, is an umbrella that holds an infinite number of processes conceived or unconceived that replicate a process that generates sound waves.

For sure, physical modeling is one, although usually limited to digital (computational) means. Before it was totally obsoleted, the Reality software synth (from Seer Systems, with an interesting but unfortunate history) had a truly excellent PM component -- Sondius WaveGuide -- with a range of capabilities from convincing woodwind simulations to wailing feedback guitars.
ndkent
Well the digital analog divide gets very tricky and not cut and dry.

Subtractive

There are digital filters, so the digital capability is not in question, though many times you will find a digital filter and the rest of a synth engine modeled after analog circuits. Modeling for sure though though electronic rather than physical

"Additive (Primarily a digital approach)"
Tell that to Buchla's 148 Harmonic oscillator sold in 1969, or those bells on Tomita's 1974 Snowflakes are Dancing. Though it is fair to say that it's lots of effort and circuits to do enough of it in Analog synths. So basically the principle was done in analog since the start but due to cost there isn't a robust engine ready to go like a digital additive synth. Though the Verbos Harmonic Oscillator based on the Buchla goes pretty far.

Fm
This gets tricky, yes it can get done in analog to an extent, but expectations are set by the variation on digital Chowning FM implemented by Yamaha on the DX7 which many argue is phase modulation resulting in the frequency being modulated. It cant be replicated with analog resources well enough. But analog users are indeed making plenty of new tones via FM Synthesis by not duplicating the Chowning via Yamaha FM.

In the early 90s, Yamaha further pushed their FM into Formant synthesis on the F1SR, one can debate if it's its own thing or an extension of something that's not simply FM

Wavetable
Primarily digital but can be done crudely with an analog sequencer as a faveform generator

Granular
Primarily digital but in theory can be done with analog delay in a simple way

Physical Modelling
As above. It's possible to do a simple waveguide with an analog delay, but it's an umbrella term

Phase Modulation
another primarily digital, Malekko did bring an analog oscillator by Wiard/Grant Richter to market with phase modulation
Addled
Thanks ndkent, that's exactly the kind of breakdown I was looking for!
ranix
re: Chowning-style FM synthesis, I disagree that it cannot be replicated in an analog synthesizer. My current 5u project (ongoing since 2014) is to create a modular analog equivalent of a DX7 and then some. I'm making rather good progress. Some of my recent posts in the 5u forum are regarding this.
Dr. Sketch-n-Etch
ranix wrote:
re: Chowning-style FM synthesis, I disagree that it cannot be replicated in an analog synthesizer. My current 5u project (ongoing since 2014) is to create a modular analog equivalent of a DX7 and then some. I'm making rather good progress. Some of my recent posts in the 5u forum are regarding this.


I didn't mean to imply that it couldn't be done. However, it requires fairly precise tuning, and that's the challenge with analog.
ranix
Very much so, I have come to learn!
qnonymouse
Miley Cyrus
cornutt
I think of waveshaping as being a synthesis technique in of itself. To me, additive synthesis uses component sines. (Or pulse waves, if you want to get into Walsh functions, which I know little about and haven't played with.) I have a play-toy that I wrote in Csound that takes an input waveform and maps it onto something like a cubic curve. Tweaking the coefficients of the curve as it plays produces radically different versions of distorted waveforms. I've thought about how to implement this in analog, but I can't think of an easy way to do it.
Dr. Sketch-n-Etch
Dr. Sketch-n-Etch wrote:
ranix wrote:
re: Chowning-style FM synthesis, I disagree that it cannot be replicated in an analog synthesizer. My current 5u project (ongoing since 2014) is to create a modular analog equivalent of a DX7 and then some. I'm making rather good progress. Some of my recent posts in the 5u forum are regarding this.


I didn't mean to imply that it couldn't be done. However, it requires fairly precise tuning, and that's the challenge with analog.

And let me elaborate further... it isn't the precise tuning that is the challenge with analog. It is when you have many identical circuits that all have to be precisely tuned together, such as the "operators" of an FM synthesis engine. The problem is that analog components are all slightly different. Every 100k resistor has a slightly different resistance. Every 10n capacitor has a different capacitance. Every TL072 opamp has a slightly different offset voltage. Every 2N3904 transistor has a slightly different beta. Etc. Etc. So, when you build 32 identical circuits to play together, they will not all behave identically, and will have to be individually and carefully calibrated. Then, every analog part has some sort of temperature response, so if the temperature in the room changes by 5 degrees, all of your careful calibration is compromised. The design has to be extremely careful, the calibration is very time consuming and tedious, and most designers have therefore abandoned analog as a possibility for such circuits, because digital circuits have none of those issues. Of course, digital circuits have their own issues. Complex logic circuits have significant timing issues which can be very difficult to get right. Microcontrollers require coding, which is an art with all that that implies (and which some of us find extremely tiresome).
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