[sdiy] Wavetable info

[James Patchell]

Guess I will have to chime in on this subject myself....

The harmonic structure of a waveform, in my opinion, is not what makes a 
sound interesting.  A pulse waveform has just about every dang harmonic you 
can imagine, but still, by itself, sounds pretty boring.  It is how the 
phases of the overtones vary with time in relation to each other is what 
makes a tone interesting.

This is the reason why I now put 3 voltage controlled filters in my latest 
synth project.  The primary thing a filter does is change the phase 
relationship of the harmonics.  It is this animation that sounds 
interesting.  And the more filters you have making changes to these 
relationships, the more interesting it sounds.

Most of you have probably heard the sound sample here: 
http://www.oldcrows.net/~patchell/synthmodulesII/index.html

But if you haven't, take a listen.  That patch uses three VCO's and three 
VCF's.  I use 3 control voltage shapers to modify an ADSR so that all three 
filters are doing something different.  The filters are in parallel, rather 
than in series.

There are some more samples here from another triple filter I did:

http://www.oldcrows.net/~patchell/synthmodules/vocalfilter.html

At 02:49 PM 1/1/2004 -0600, David Cornutt wrote:

>On Thursday, January 1, 2004, at 01:50  PM, Scott Gravenhorst wrote:
>
>>Hi all, and Happy New Year.
>>
>>I've often thought that it would be interesting to do waveform drawing,
>>but I've also wondered just how useful it is ?  For what I know, a static
>>waveform is just a pile of harmonics, regardless of whether it's generated
>>by a waveform specific VCO or a hand drawn deal.  If the harmonics don't
>>change in some way over time, then the waveform itself is not interesting.
>
>To avoid cluttering up the list with a discussion that has already 
>cluttered up
>Analogue Heaven, I'm going to avoid the "what makes a good oscillator"
>philosophical discussion and stick to some technical aspects...
>
>It's more correct to state that any static waveform is a pile of overtones.
>With the waveforms that we commonly use in (particularly) analog
>synthesizers, the overtones have a particular harmonic structure.  You
>can change this to an extent with a filter, but beyond a certain point
>it becomes very difficult to do with subtractive synthesis.  Consider, for
>example, what fixed filter banks do; they create a pattern of peaks and
>valleys in the Fourier transform that may look very different from what
>originally went in to the filter.  These are typically used for fixed formats,
>but what if you want them to track pitch?  Building a set of 15 or so good-
>quality VCFs, and getting them all to track together, could be a very
>expensive undertaking.

         -Jim
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