[sdiy] Modulation waveforms

[Ian Fritz]

At 07:31 AM 7/5/2010, Scott Gravenhorst wrote:
>Tom Wiltshire <tom at electricdruid.net> wrote:
> >I've spent a lot of time the last couple of years developing
> >uP-based modulation sources of one type or another. I thought
> >some of you might be interested to see the results of my work in
> >this direction. My personal preference is for the random
> >waveforms, and I especially like the fact that they have an
> >underlying frequency, despite being random in some sense. This
> >lets you set up slowly varying sounds that don't just go
> >"woowoowoowoowoo".
>
>Yes, random waveforms!  I too have in some of my designs a "random LFO"
>which is really noise (from a 64 bit LFSR) through a lowpass filter,
>usually just a simple single pole IIR, but I've also used a state
>variable (2 pole) filter with resonance control for a more defined
>frequency with randomness.  I far prefer these to the woowoowoo kind of
>modulation acheived with non-random waveforms.  It sounds, for lack of a
>better term, more natural.

There are a lot of interesting possibilities for making chaos generators in 
micros.  Most of the continuous systems such as the ones I have been 
working with in the analog domain have companion discrete "maps" with 
simple generating rules.

Also I'm having fun playing with some billiard-like systems.  With the 
simple systems I've been studying the waveforms appear to be periodic but 
often with extremely long repeat periods.  In computer simulations I have 
seen patterns with local densities of ~ 5e4 (corresponding to thousands of 
bounces around the "table" for a single period.  In a micro one could use 
more complicates ruled for the trajectories, and probably get the more 
usual true "pseudo chaotic" behavior.

Some initial results in this e-mus thread:
http://electro-music.com/forum/viewtopic.php?p=290413#290413

Ian