Interesting Paper available on Moog VCF

[Don Tillman]

   Date: Wed, 18 Sep 1996 11:15:17 +0200
   From: thierry.rochebois at ief-paris-sud.fr (Thierry Rochebois)

   >You seem to be suggesting that this algorithm is used in the Nord
   >Lead,

   No, I just say that the NordLead is an example of this kind of
   implementation.  I do not think that the researches from Clavia are
   published anywhere. 

What do you mean by "implementation"?  Stilson&Smith's paper never
mentions any hardware; it was probably never built.  The paper is
about analyzing some of the issues of pole location.

   You know, many "industrial" researchers are not famous and never published
   anything in any conference... My example is Ralph Deutch, he worked for
   Kawai and patented more than 136 devices... And nobody knows him.

A patent *is* published, that's the point of it!

   I played the Nord Lead in a shop once.
   I tried many things to hear some problems related to digital.
   For example, I opened the filter and transposed any waveform at its
   maximum (including transpose and pitch bend)... and I didn't hear any
   aliasing... 

Not being able to hear aliasing (which has more to do with waveform
generation anyway) in a music store environment is a far cry from
having the full-tilt "gazorch" and "balls" of the Moog VCF.

   Nonlinearities are not very hard to implement in digital form..
   Perhaps another paper will show this kind of implementation.

Analog nonlinearities are extremely difficult to implement digitally.
When you add a digital nonlinearity you create an infinite number of
harmonics, and these alias around and sound pretty crappy.

  -- Don