Karplus-Strong Physical Modeling Synthesis On The Sequential Pro 3

Here’s a demonstration, via ToyKeeper, of a Karplus-Strong synthesis patch on the Sequential Pro 3.

Karplus–Strong string synthesis is based on using very short filtered delays to create sounds similar to plucked strings or hammered percussion.

The video is not intended to be a performance or a tutorial, but simply to demonstrate the variety of sounds that are possible with this type of patch.

Here’s an example of using the patch to create legato sounds, closer to a synth lead or an electric violin:

Here’s the details of the patch:

To make a patch like this, basically just start with an init patch, turn off the oscillators, route a plucky aux envelope to the noise level, and turn on tuned feedback (amount = ~62 to ~64, tuning = 24). The rest is just performance conveniences, like the mod wheel, aftertouch, pitch wheel… and some delay.

Create an “exciter”:
– Create an init patch (OctDown + Latch).
– Turn off all the oscillators in the mixer.
– Map aux 1 env to noise level.
– A:0, D:3, S:0, Amt: 127
– Set the filter to state-variable lowpass, cutoff ~874, no resonance

Add feedback:
– Enable Tuned Feedback: Amt +61, Tune 24 (Amt varies with temperature)
– Map Slider to Feedback Amt, +4
– Enable Slider latch, and slide it to control whether note grows or fades over time.
– Increase the range which is in tune: Map Note Num to Feedback Tune, +2 (may require adjustment on each Pro 3)

– Map LFO1 to Feedback Tuning
– Map Pressure to LFO1 Amt, +1
– LFO1 Freq 110, Amt 0, Shape triangle
– Map Note Num to LFO1 Freq, +57

– Map ModWheel to Distortion, Amt +127

– Map PitchBnd to Cutoff, +58
– Map PitchBnd to Feedback Tune, -2

– Enable effect 1: DelayStereo, FX Mix 40
– Sync On, Sync Freq 8, Feedback 110, LPF 140

Check out the video and share your thoughts on Karplus-Strong synthesis in the comments!

14 thoughts on “Karplus-Strong Physical Modeling Synthesis On The Sequential Pro 3

  1. Not hating on the video, but my general thoughts on KS are that it’s slightly overrated. It just doesn’t sound very good to me, but I suppose it can be useful to know about in a pinch in the same way that it can be useful to play a filter if you need an additional oscillator. Would be interesting to hear KS with linear FM or some other combos like that!

    1. It’s important to understand that this is only a very basic form of physical modelling, even a simple model of a guitar string requires two carefully calibrated delays feeding back into each other so as to simulate the input position on the string, then you’d typically want one or more pick-up positions too – all of these impact the timbre significantly.

      There’s 20 years of research into how to accurately model how the exciter interacts with the string or pipe: a bow is different from plucking, itself different from blowing a trumpet or the single reed of a clarinet or the double-reed of an oboe. None of these can be modelled on a standard synth, though the inclusion of tunable delay-lines is great fun to help create a more organic sound.

      Hopefully KORG or Yamaha will bring back a proper physical modelling synth!

  2. Understand the criticisms, but it blows me away that this is possible on the Pro 3. I’ve got a Pro 1 and didn’t understand that the Pro 3 was such a leap forward in terms of what it can do.

  3. There was a moment where I started to hear a kind of bowed cello or double-bass sound, which is pretty difficult to simulate with subtractive. If this is thought of as a way to generate an oscillator shape and then run through another stage, such as formant filters or convolution, it’s a perfectly valid form of synthesis– with its own unique qualities.

  4. I wish more delay units/plugins/etc had more precision with delay times or had a “precision mode” along with the ability to scale delay time via MIDI key-tracking so you could do this with more gear.

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