[sdiy] Karplus-Strong overblowing?

[Mike Bryant]

It wasn't an electrical system, they were simulating a huge chemical plant.  Any length of pipework is like a transmission line with inductance, resistance and some capacitance.  Changes in diameters cause drops in pressure but not necessarily energy loss - capacitance, and the chemicals are like electrons only larger.  Pumps are like power sources and air is resistance.  By breaking the system into small sections you could simulate it in a discrete time mode - digital.
You used to use the result all the time - washing machine powder.  Fortran programs used to run as background jobs on the mainframe for weeks or months on end - definitely not real time audio 🙂

Simulating microwave r.f. Filters was first done from the 1970s.  Definitely very abstract level - but it increased the chance of the first r.f. prototype at least functioning.  These filters often only had a dozen components, but the most critical one was actually the transmission line etched into the PCB.  Those who got that regularly right became high paid r.f. gurus, everyone else went into audio or other low frequency work like telephony, vhf, etc.

Me I avoided both and went into digital 🙂

You are correct about overblowing - but it depends on the instrument.  A flute only produces 'nice' harmonics, but a harmonica produces fifths, octaves and possibly lots of other intervals as the harmonica is only part of the resonant structure, whereas with a flute all you can do is create different standing waves in the cylinder, your mouth being mostly isolated by the right angle entry point.  Other wind instruments are somewhere in between.  Put a microphone/ADC on a school recorder and do an FFT on the output - you can create many notes without even using your fingers simply by shaping your lips, and they use the single hole on the backside to move them a bit.  Then overblow and you'll move up an octave - but not quite.  Recorders are that good an instrument.




________________________________
From: cheater cheater <cheater00social at gmail.com>
Sent: 04 January 2026 23:24
To: Mike Bryant <mbryant at futurehorizons.com>
Cc: Synth DIY <synth-diy at synth-diy.org>; Josh Nursing <josh.nursing at gmail.com>
Subject: Re: [sdiy] Karplus-Strong overblowing?

Mike, any place I can read your wife's papers?

If Fettweis filters were used to simulate analogue filters before
digital could be used, how were those filters simulated if not
digitally? Or was this some sort of other, "higher level" simulation
(still digital, but eg not simulating the single electronic components
separately)?

Mattias, overblowing does not create octaving, it creates an overdrive
and a brighter sound while suppressing the fundamental. So odd
harmonics are not being removed by overblowing like you describe. I
suggest looking up demos of overblowing of brass instruments on
youtube.

Richie, some great comments and very useful and interesting. Those
"Reed Tables" sound like Volterra kernels.

Thanks

On Sun, Jan 4, 2026 at 6:51 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> Yes the Fettweis filter was used in simulating analogue filters for r.f. long before one could consider actually doing it digitally.  Avoiding hacking the PCB transmission line with a scalpel quite so much, adding 1pf capacitors or adding/removing a turn on a spring.
> ________________________________
> From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Josh Nursing via Synth-diy <synth-diy at synth-diy.org>
> Sent: 04 January 2026 17:20
> To: Synth DIY <synth-diy at synth-diy.org>
> Subject: Re: [sdiy] Karplus-Strong overblowing?
>
> And I made a mistake myself. The other tech is named "Wave Digital Filters", not "Waveguide Digital Filters".
>
> They were developed by Fettweis quite a long time ago.
>
> Josh
>
> On Sun, 4 Jan 2026 at 12:10, Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> With modern processing meshes probably are applicable to audio as well now.  But they originated in other much slower system simulations which is where all the underlying maths was developed, partially by my wife long before they were called that 🙂
>
> And I never said 'Waveguide Digital Networks' - that was someone else and is a bit meaningless.
>
> But to me stating Digital Waveguides without the word Network implies a series of parallel waveguides with different characteristics possibly all summed into one at the end, nothing more.
>
>
> ________________________________
> From: Josh Nursing <josh.nursing at gmail.com>
> Sent: 04 January 2026 17:01
> To: Mike Bryant <mbryant at futurehorizons.com>
> Cc: Synth DIY <synth-diy at synth-diy.org>
> Subject: Re: [sdiy] Karplus-Strong overblowing?
>
> No, no, there are Digital Waveguide Meshes for audio and sound synthesis too.
>
> They're fairly more complex to implement and very processing power-hungry, but they're used for, among other things, surface modeling for Physical Modeling or Drums and other percussive instruments.
>
> As you can probably imagine, the junctions start getting more connections than in the simple D.W..
>
> Josh
>
> On Sun, 4 Jan 2026 at 11:41, Mike Bryant <mbryant at futurehorizons.com> wrote:
>
>
> However  the term outside of audio is Digital Waveguide Mesh.
>
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20260104/72f2042f/attachment.htm>