# PHYSICAL MODELLING: your approach, your knowledge and ideas



## GiuseppeS+OS (Feb 24, 2019)

Hi everyone,
among all the sound design techniques I use, I find physical modelling the most fascinating one. The process itself of reproducing the behaviour and the physics of an acoustical instrument is to me like creating a surreal version of something real, decomposing it into its sonic characteristics and take control of each one of them to create something new. It's like augmented reality in the realm of sound.

It'd be great if we would share resources (articles, videos) about physical modelling, from the most "basic" digital waveguide approach to the most recent research in Finite Differences Time Domain (which is used in Madrona Labs' Kaivo). 
And of course feel free to share your work and your preferred synths and softwares based on physical modelling  
I found this one pretty interesting


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## Chandler (Mar 4, 2019)

I love physical modeling, but unfortunately there doesn’t seem to be much info on it. It seems to be a forgotten form of synthesis that most developers don’t want to deal with. Now I’m beta testing a synth that can do physical modeling and I’m really excited about it. On another forum I wrote a lot of physical modeling and I’ll post it here if people are interested. 

Anyway AFAIK there are only 2 types of PM, Karplus-Strong and modal synthesis. Waveguides are just an extension of KS and are actually fairly complex.The FDTD methods seem to be the same as waveguides, but done in a different way math mathematically. I don’t know for sure though, but they do sound the same.

I want to make some videos on physical modeling the future and I’ll post them here if people are interested. I’m not a scientist, so they’ll be more of a practical guide.


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## d.healey (Mar 4, 2019)

Additive synthesis is the approach that I think produces the most realistic PM instruments.

A few developers have created very good woodwind PM instruments and some okayish brass ones. I have yet to hear any really good PM bowed strings.

This is one of my favourite sounding PM woods - https://www.native-instruments.com/en/reaktor-community/reaktor-user-library/entry/show/12303/


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## GiuseppeS+OS (Mar 5, 2019)

Chandler said:


> I love physical modeling, but unfortunately there doesn’t seem to be much info on it. It seems to be a forgotten form of synthesis that most developers don’t want to deal with. Now I’m beta testing a synth that can do physical modeling and I’m really excited about it. On another forum I wrote a lot of physical modeling and I’ll post it here if people are interested.
> 
> Anyway AFAIK there are only 2 types of PM, Karplus-Strong and modal synthesis. Waveguides are just an extension of KS and are actually fairly complex.The FDTD methods seem to be the same as waveguides, but done in a different way math mathematically. I don’t know for sure though, but they do sound the same.
> 
> I want to make some videos on physical modeling the future and I’ll post them here if people are interested. I’m not a scientist, so they’ll be more of a practical guide.


Thank you Chendler! Sure, feel free to post anything related with Physical Modeling. In regard to FDTD, I 've read some papers with the mathematical scheme , I don't know how this is actually implemented, as long as I know there're not many instruments using this technique. As I said, feel free to share content in the thread, it could be a great opportunity to make this thread a resource for anyone interested in the topic


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## GiuseppeS+OS (Mar 5, 2019)

d.healey said:


> Additive synthesis is the approach that I think produces the most realistic PM instruments.
> 
> A few developers have created very good woodwind PM instruments and some okayish brass ones. I have yet to hear any really good PM bowed strings.
> 
> This is one of my favourite sounding PM woods - https://www.native-instruments.com/en/reaktor-community/reaktor-user-library/entry/show/12303/


Thank you David! I didn't know about this Reaktor Instrument, will download it and give it a try for sure


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## d.healey (Mar 5, 2019)

Forgot to mention Pianoteq which I believe is completely PM.


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## mgpqa1 (Mar 5, 2019)

A pair of interviews with Marc-Pierre Verge and Philippe Dérogis (the co-founders of Applied Acoustics) are pretty informative and interesting:
https://www.applied-acoustics.com/techtalk/physicalmodeling/
https://www.applied-acoustics.com/techtalk/aastech/


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## Nick Batzdorf (Mar 5, 2019)

d.healey said:


> This is one of my favourite sounding PM woods - https://www.native-instruments.com/en/reaktor-community/reaktor-user-library/entry/show/12303/



It says you need to run it at 88.2 or 96K for it to be in tune. Is that true?


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## d.healey (Mar 5, 2019)

Nick Batzdorf said:


> It says you need to run it at 88.2 or 96K for it to be in tune. Is that true?


I haven't used the latest version so I don't know.


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## Chandler (Mar 7, 2019)

Here is an interesting video on modal synthesis and sound design. 


Its such an intersting style of synthsis, I don't know why it isn't used more often.


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## Paul Grymaud (Mar 7, 2019)

Physical modelling ?


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## timprebble (Mar 8, 2019)

I really enjoy messing with Mutable instruments ELEMENTS module

https://mutable-instruments.net/modules/elements/


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## Joe_D (Mar 8, 2019)

Chandler said:


> Here is an interesting video on modal synthesis and sound design...Its such an intersting style of synthsis, I don't know why it isn't used more often.



As presented in that video, it is highly limited; it mainly works for shorter and more percussive sounds. In the sound of, say, an oboe or violin, many partials persist throughout the sustain of a note, and they vary in pitch (and phase) as well as amplitude. Some partials may also come and go during that sustain. Full-on additive synthesis is required to accurately produce sustained sounds like those.

Also, the filter-based variations they use do work for the simple percussive video game sounds, but in "real" sounds, the number and amplitude of partials increases in a complex (and probably non-linear) way as dynamics change; I don't think modal synthesis would work well for that.

In a way, you could somewhat compare the sound generation in that video to the second generation of digital synthesizers (Korg M1 era), where a short sampled attack was often layered with a synthesized sustain. It was cool at the time, but nowhere near realistic.

I'm not saying that the whole idea of modal synthesis is not worth exploring; more complex modelling of resonant structures, as in the Mutable example above, could produce very interesting sounds.


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## Wally Garten (Mar 8, 2019)

GiuseppeS+OS said:


> like creating a surreal version of something real



Yeah -- this is my favorite use for PM synths! (I'm not up to speed on the math, and can only comment on various PM synths as a user.) I use both Sculpture and Chromaphone fairly often to create really interesting, "surreal" percussion, and sometimes winds. PM percussion, in particular, can be really beautiful. And you can get some lovely sounds that fall between categories -- something that sounds partway between a flute and a bowed crotale, say. That's my favorite.

I also have String Studio, which I'm still learning, but, in line with @d.healey's comment above, I think the plucks are more convincing than the bowed sounds. 

And then there's Kaivo, which I have not found particularly user-friendly. I _want_ to like it, but I think the mix of granular synthesis, PM, and modular patching just makes it hard to know what you're going to get. There may be some conceptual key I'm missing that would make it easier. Still, you can wring some pretty cool noises out of it -- the sort of metallic sound that's keeping 5/4 time at the beginning of this track is Kaivo.


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## GiuseppeS+OS (Mar 8, 2019)

timprebble said:


> I really enjoy messing with Mutable instruments ELEMENTS module
> 
> https://mutable-instruments.net/modules/elements/


I'm intrigued with Mutable Instruments, is this a Karplus Strong based module?


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## timprebble (Mar 8, 2019)

GiuseppeS+OS said:


> I'm intrigued with Mutable Instruments, is this a Karplus Strong based module?



modal synthesis - explained at that link: "Elements combines an exciter synthesis section generating raw, noisy sounds characteristic of bowing (filtered friction noise), blowing (pitch-controlled granular noise), or striking (stick, mallet, hammer or brush sample playback… or bursts of synthetic impulsions) These sources, or external audio signals, are processed by a modal filter bank – an ensemble of 64 tuned band-pass filters simulating the response of various resonant structures (plates, strings, tubes…) with adjustable brightness and damping"

*Excitation signal generator*

Three generators with mixer: bowing noise, blowing noise, percussive impulses.
Envelope contour for bowing and blowing.
Bowing noise generator: particle-like scratching noise with 2-pole low-pass filter.
Blowing noise generator: granular pitched noise with wavetable-like scanning between various tone colors.
Percussive impulse generator: interpolates through a collection of impulsive excitations – including sampled sticks, brushes and hammers, and models of damped mallets, plectrums, or bouncy particles. 2-pole low-pass filter and pitch control.
*Modal resonator*

Internally uses 64 zero-delay feedback state variable filters.
Coarse, fine and FM frequency controls.
Geometry: Interpolates through a collection of structures, including plates, strings, tubes, bowls.
Brightness. Specifies the character of the material the resonating structure is made of – from wood to glass, from nylon to steel.
Damping. Adds damping to the sound – simulates a wet material or the muting of the vibrations.
Position. Specifies at which point the structure is excited.
Space. Creates an increasingly rich stereo output by capturing the sound at two different points of the structure, and then adds more space through algorithmic reverberation.


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## Chandler (Mar 9, 2019)

Joe_D said:


> As presented in that video, it is highly limited; it mainly works for shorter and more percussive sounds. In the sound of, say, an oboe or violin, many partials persist throughout the sustain of a note, and they vary in pitch (and phase) as well as amplitude. Some partials may also come and go during that sustain. Full-on additive synthesis is required to accurately produce sustained sounds like those.
> 
> Also, the filter-based variations they use do work for the simple percussive video game sounds, but in "real" sounds, the number and amplitude of partials increases in a complex (and probably non-linear) way as dynamics change; I don't think modal synthesis would work well for that.
> 
> ...



Modal Synthesis is generally used for percussive sounds not clarinets or flutes. Although its possible to do there really isn't much of a point because other methods work better for those sounds. Waveguides are a better alternative if you want to model woodwinds, brass or even strings. I'm not sure how familiar you are with modal synthesis, but it can do more than what is shown in that video. The video just shows some very important and unique things it can do. 

The problem with additive synthesis is it doesn't respond in a natural way, so it takes a lot of programming to get right. On top of that it doesn't contain noise which is a component in almost all natural sounds. The decay rates of the partials have to be programmed in and adjusted for each note, but proper partial decay is easily achieved with modal synthesis.Another problem with additive synthesis is that, like you said, you need to layer transients to get the initial attack correct most of the time.

Don't get me wrong I love additive synthesis, but it can't replace or replicate the sounds of modal synthesis easily or well. All forms of synthesis have their strengths and weaknesses.


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## Chandler (Mar 9, 2019)

timprebble said:


> I really enjoy messing with Mutable instruments ELEMENTS module
> 
> https://mutable-instruments.net/modules/elements/



That's an awesome modal synth. I think softtube makes a vst version for their modular vst. Its a shame there aren't more modal vsts available, I believe there are only 3 or so.


On another note, I'm so disapointed in Yamaha for not continuing development on their VL1 synth.
That synth came out in the early 90s I believe and IMO still sounds amazing. If they would have kept working on it I'm sure it would sound even more realistic now.


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## d.healey (Mar 9, 2019)

Chandler said:


> Don't get me wrong I love additive synthesis, but it can't replace or replicate the sounds of modal synthesis easily or well. All forms of synthesis have their strengths and weaknesses.


At the point in the video around 1:09 where he says - "We synthesize the sinusoids" - would that be done by additive synthesis?


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## Chandler (Mar 9, 2019)

d.healey said:


> At the point in the video around 1:09 where he says - "We synthesize the sinusoids" - would that be done by additive synthesis?



It could be. For modal synthesis it is done with bandpass filters, but the filters produce sinusoids. I have no idea how they did it in the video. It could be additive or bandpass filters. Sometimes they can sound the same, but each does certain things better than the other.


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## Nick Batzdorf (Mar 9, 2019)

Chandler said:


> On another note, I'm so disapointed in Yamaha for not continuing development on their VL1 synth.


 
I have one and love it.

But what I like best about it is less the emulations than its ability to create acoustic instruments that don't exist yet sound like they could.

Yamaha had a hard time selling it because - as Avery Burdette, a product specialist (I think that was his title?) at Yamaha said - it sounded broken in the store to people who didn't know how to make it work.

And yes, it was released in 1994. It's a major accomplishment in the history of synths.


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## dflood (Mar 9, 2019)

I tried out this Serenade Reaktor instrument about a year ago:
https://www.native-instruments.com/en/reaktor-community/reaktor-user-library/entry/show/7463/

There's a great tutorial here for using it with a Leap Motion controller:
http://blog.leapmotion.com/playing-a-virtual-violin-with-serenade-geco-midi/



I quite liked the tone but as I recall the playability was limited - it's been a while since I messed with it but I think there was no polyphony and limited note duration.

Edit: This was also developed by Chet Singer, who made the Silverwood Flute mentioned earlier.

Edit 2 : I just looked at the Native Instruments Reaktor User library page and see there are a couple of newer iterations of the Serenade instrument which I need to try out:
https://www.native-instruments.com/en/reaktor-community/reaktor-user-library/instrument/1/3/


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## timprebble (Mar 31, 2019)

new physical modelling synth RESPIRO, "for Wind, Breath and MPE controllers"
https://www.imoxplus.com/site/


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## GiuseppeS+OS (Apr 1, 2019)

timprebble said:


> new physical modelling synth RESPIRO, "for Wind, Breath and MPE controllers"
> https://www.imoxplus.com/site/



This sounds really interesting. Will have a look on the website to today and try to understand what's the specific technique behind it. Thanks Tim!


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