Month: May 2019

Lockhart Wavefolder

I’d like to share a Csound user-defined opcode port of the “Virtual Analog Model of the Lockhart Wavefolder” by Fabián Esqueda, Henri Pöntynen, Julian D. Parker and Stefan Bilbao that was presented at SMC 2017. The paper reference is:

F. Esqueda, H. Pöntynen, J. D. Parker and S. Bilbao, “Virtual Analog Model of the Lockhart Wavefolder”, in Proceedings of the 14th International Sound and Music Computing Conference (SMC-17), Espoo, Finland, July 5-8, 2017, pp. 336—342.

The authors have placed a website with the original paper, errata, and a Max/MSP/gen~ implementation at:

I have converted the gen~ code to a Csound user-defined opcode and placed the code and test file here:

The test instrument follows the recommendations of the paper to use a cascaded wavefolder structure with input gain and DC offset parameters. (See figure 9 in the paper.) The sampling rate is 88.2khz as mentioned in the paper to deal with anti-aliasing issues without having to use oversampling.

An example render of the test CSD file is below, modulating both the gain and DC offset parameters:

I’m very excited by all of the wonderful sonic possibilities! Bravo to the original authors for their work!

Additive Pitch Rhythms Using Hexbeat

Practice session today using additive pitch hexbeat rhythms to generate melodic contours.

Each hexbeat() is generating sequences of 1’s and 0’s which are then multiplied to alternate between things like 7 and 0.  So if I add one that alternates between 2 and 0, I get 9,7,2, and 0 as possibilities.  Then with say 4 and 0, I get additional combinations.  With the patterns of different lengths (I’ve been using mostly prime number lengths) it generates a nice long overall pitch pattern, which is then masked by the rhythmic hexplay() pattern.  I then add a choose() to say “play 70% of the time” and I find all of that together is quick to write, generates good variety, but has an underlying structure that is stable.  (It’s been on my mind how to mix randomness + stability in interesting ways and I’ve found these explorations have been leading to some interesting pattern generation.)

This desmos graph visualizes an example of a 3-part hex pitch rhythm added together:

(Click on the “Edit on Desmos” link in the graph to turn on/off visualization of the various individual hex pitch rhythms.)