This module uses Karplus-Strong synthesis, which is a type of string physical modeling that uses a delay line with a lot of feedback to create periodic waveforms out of a short burst of noise.

In this ground-up remake of the library Karplus-Strong VCO module, I was looking to expand the sweet spots of each parameter and balance the knobs so that every nudge makes a difference. To further enhance the string-like quality of this voice, there are 4 delay lines set up in a round-robin meaning each note plucked will ring out without being cut off. This is similar in behavior to the popular Mutable Instrument’s Rings module.

Overall, a great choice for making plucked sounds both subtle and bold.


Input Signal Range Notes
34%20PM80x75 0 to 1 trigger input
38%20PM78x74 -5 to 5 1/Oct Input

Output Signal Range Notes
41%20PM71x74 -1 to 1 If saturation is turned up and all voices are active, there is a chance that the signal can go past 1. If this is the case, attenuating the signal will remove any resulting distortion.


Knob, Button Function Notes
44%20PM143x121 Feedback This is the primary way to control the decay of the algorithm.
49%20PM131x127 Saturation This is a soft clipping algorithm that had the effect of compressing the signal and emphasizing the volume of the decay.
02%20PM129x116 Exciter Decay By shortening the decay of the noise exciter you can create accented plucks.
11%20PM137x108 Frequency Cutoff The cutoff frequency of the low pass filter of the noise exciter is running through can change the type of material the string is made from. The higher the cutoff the more metallic the string sounds.
18%20PM125x100 Exciter Mode Toggles between unipolar and bipolar noise exciters.

Version History

Revision File Date Notes
2.0 uKarplus-StrongV2.audulus (35.1 KB) 2018/0710 Updated to have overlapping decays and extended timbral controls.


Revision File Date Notes
1 finger-picking.audulus (180.1 KB) 2018/07/10 Combining uK-S with the Citrus Seq yields some pretty chill vibes.

Absolutely amazing. What an accomplishment!!

The most realistic music from a modular system I have ever heard.

Just Wow!


I totally agree - the demo here has some really great chords going on ringing out in a nice way. Love the round-robin polyphony! :slight_smile:


Really clever use of polyphony and a great sound! Great design. :cowboy_hat_face: