[sdiy] [AH] What would the ultimate LFO do?

[Andrew Simper]

On 18 December 2011 15:51, Mark Rivera <marr at lumin.us> wrote:
> My fav has to be Oakley Little LFO. It has a Shape control which skews
> the tri/pulse wave left or right in time, and has sync input. Would
> like to see Rate and Shape CV inputs, and a built-in 3-to-1 mixer.

I've just gone through the design process for doing a dsp based LFO.
Some of the cool shapes I dreamt up didn't actually sound very musical
for modulating the cutoff frequency of a filter, or pitch of an
oscillator. I wanted something with as few controls as possible, where
all controls could be modulated with smooth results and musical
transitions. In the end I came up with a design which is basically an
MS20 or Oakley Little LFO but with swing and a smooth variable
exponential transition between triangle and sqr waveforms:

Rate - bpm synced or hz from 0 hz to 16 hz
Rate Scale - control input that increases the base rate so you can
modulate this but than come back to the original rate easily, x1 to
x65k
Width - changes from saw up to triangle to saw down
Exp - changes from inverse exponential shape, through linear to exponential
Swing - alternates the length of each alternate cycles but keeps the
total cycle time to two cycles
Rand - random sample and hold amplitude of next waveform endpoint
Phase - phase when triggered
Offset - stereo offset of second lfo

It looks like this: http://www.cytomic.com/files/dsp/thedrop-lfoshapes.pdf
And sounds like this: http://www.cytomic.com/files/thedrop-morphinglfo.mp3

Andy