Modular Diary – 028

I came across the Rob Hordijk’s Rungler in the Audulus forum a while ago and that particular module, as well as his system and approach in general, is something that I find myself repeatedly returning to.

The Rungler also forms the core of his Benjolin and Blippoo cicuits, and one element of it that I’ve found particularly fascinating is his Fluctuation modulation – a kind of combined FM/AM modulation that seems to have grown organically out of a double integrator algorithm used to round off the edges of a triangle wave. I haven’t quite figured out how to implement that algorithm directly in Audulus, but I did figure out that the edges could be rounded off a triangle wave in Audulus using the tanh (hyperbolic tangent) expression with similar results, and with that as a basis simply coupled regular AM and (linear) FM modulation to imitate Hordijk’s fluctuation – the only trick being to invert the AM signal so that the highest points of the FM correspond to the lowest points of the AM. Looking at the resulting waveform in a scope seems to come close to what Rob shows in this video around 16m10s.

Fluctuation is also used in Hordijk’s Triple LF-VCO and the result is an “extremely natural sounding vibrato, much gentler than with a normal LFO”, as explained on the Rob Hordijk information site.

I posted my first, somewhat rough, tryout in the Audulus forum a while ago and I’ve since been trying to refine the patch and experiment a little with what it sounds like at different frequencies. Robert Syrett has already put together something approaching a Benjolin (and a Rungler), and as the next steps in my own learning process I’m looking forward to figuring out my own implementation of a little more of the Rungler cicuit.

Modular Diary – 028: I came across the Rob Hordijk’s Rungler in the @Audulus forum a while ago and that particular… rdgr.me/u/cxvgqn

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Rudiger Meyer is a composer interested in the play between traditional concert music and new media.


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