[sdiy] Karplus-Strong overblowing?

[Mike Bryant]

Actually from JOS
"A Digital Waveguide<http://en.wikipedia.org/wiki/Waveguide> Network (DWN) consists of any number of digital waveguides interconnected by scattering junctions<https://ccrma.stanford.edu/~jos/pasp/Scattering_Impedance_Changes.html>"

However  the term outside of audio is Digital Waveguide Mesh.
________________________________
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 16:24
Cc: Synth DIY <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Karplus-Strong overblowing?

The term is Digital Waveguides not 'Waveguide Digital Networks'. J.O.S. is definitely the Canonical reference online although there's a massive amount of maths involved in his texts.Perry Cook also does some very good texts on those types of structures including wind instruments.

Get the structure right, and you'll probably find that the overblowing behaviour is then totally emergent from the model itself.

DWs were used in Yamaha VL1 and VP1 (later VL70m too) AFAIK.

It's fun stuff with particularly interesting tones for me but I do not necessarily look for emulative acoustic tones but rather Synthetic/Electronic tones with some 'material / structural realism' built-in. In other words, 'Syncoustic'.

Regards,

Josh

On Sun, 4 Jan 2026 at 09:03, Mattias Rickardsson <mr at analogue.org<mailto:mr at analogue.org>> wrote:
Richie  -  Good points about the need of nonlinearities and the advice about Waveguide Digital Networks.

Overblowing should result in octaving behaviors, right? Then it's not enough to suppress the fundamental, but all the odd partials should get weaker and the even ones (the next octave) get stronger. Some nonlinearity then needs to favor the even ones.

/mr




Den lör 3 jan. 2026 13:48 <rburnett at richieburnett.co.uk<mailto:rburnett at richieburnett.co.uk>> skrev:
The original KS model is very basic as others have said. It really just
models a single "round trip" delay with some (frequency-selective)
damping and possibly some dispersion in the loop. That's fine for
modelling things that are struck or plucked with transients like
strings.

I believe wind instruments are more accurately modelled by Waveguide
Digital Networks. These are networks of bi-directional delay lines
coupled together by "scattering junctions." The scattering junctions or
nodes determine how much of the output of one delay line couples into
the next, how much reflects back into the original delay line
(propogating in the opposite direction,) and how much is absorbed (lost
to heat, radiated, whatever.)

Then at the ends of the model you have non-linearities that control how
the pressure waves interact with the Reed and blowing pressure at the
blown end of the instrument, and the outside air pressure at the, erm,
bell end ;-))

I think its these non-linearities at the ends that will be critical for
modelling overblown behaviour.  The overall model must be non-linear if
the behaviour changes when the amplitude of the excitation changes.
Otherwise the strongly blown sound wound just be a louder, but otherwise
identical, version of the softly blown sound. There wouldn't be a shift
to a different resonant mode when over-excited.

Waveguide Digital Networks and physical modelling aren't really my
thing, so i wont say any more as could be misleading or plain wrong. I'd
do some reading of the physical modelling literature by Julius Orion
Smith if you're into the theory. Or alternatively string together some
delay lines and play about with scattering nodes, filters and
non-linearities at the ends if you're into the practical/coding side.
"Reed tables" appear to be one way to model the non-linear behaviour of
the reed to pressure differences.

I hope this is some help. Interested to read other's comments and
suggestions.

-Richie,


>>> Am 02.01.26 um 10:56 schrieb cheater cheater via Synth-diy:
>>>> Does Karplus-Strong synthesis allow for overblowing? Are there any
>>>> modifications to it that allow it?
>>>>
>>>> Overblowing is when you blow into a reed instrument too hard and
>>>> essentially the fundamental becomes much weaker and the higher
>>>> partials become much stronger, kind of "overdriven".
>>>>
>>>> Thanks
>>
>>
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