[sdiy] Poly analog synths needing multiple signal paths?

[Andrew Simper]

On 9 October 2013 02:37, Olivier Gillet <ol.gillet at gmail.com> wrote:
>> I would think that you could have multiple oscillators, each getting its own CV, feed them into a mixer, then from there to filtering etc.
>
> This can be done, this is called paraphony.
> ...
> You play and hold a C. The envelope is triggered. And you hear a C
> with a ptzong filter sweep, and then it sustains at a low level.
> Now you play a G, one second later. Either:
> a/ The envelope does not retrigger and you won't hear anything.
> b/ The envelope retriggers and you hear the C+G with the filter sweep.
> This is like the C has been retriggerd.
>
> Another problem is filter key-tracking. If you play a low note and a
> high note at the same time, you probably want the two of them to go
> through filters with different cutoff values so that they have a
> relatively homogenous timbre.
>
> Olivier

Another problem is intermodulation distortion of different pitches in
a chord all hitting the same non-linear filter. In many non-paraphonic
synths a lot of the tone comes from the filter drive which distorts
the oscillators and make things sound more interesting, but with a
paraphonic setup this gain staging will cause intermodulation
problems.

Andy