EGs

[Martin Czech]

> i'm planning to build a machine which will produce sounds continuously
> evolving and morphing one into another (pardon my english). so, rather
> than have a usual saw/pulse/tri alternative, i'd like to make something
> which would continuously morph between these. so far, the only idea that
> comes to my mind is to feed an EG with a pulse. in theory, i'll have six
> parameters (pitch, pw, adsr) to play with, but will this work in real
> world? will i have to make my own egs (oh, no!) or it's possible with
> existing chips?
> 
As far as the ADSR is fast enough, that should be no problem. 
Of course, you will have to track all time parameters together
with frequency a bit, to avoid silence at higher frequencies.
I doubt if this will sound really exiting.

CEM had once a more elaborated wave shaper. Have a look at
"http://www.synthtech.com/" etc.

I toyed arround with those waveshaping ideas for a while:

Analog:
A1.: Waveshaping could be easily done with a picewise linear funktion, 
    (e.g. using a tri wave as input). I've hever seen that in a synth up to now.
    Just a few op-amps, but not so easy to
    predict the output. If there is an interest for such a circuit,
    I could send an asciimatic of the principle cell, it's really easy
    and it's voltage controlled.
    Other possibilities are clipping, unsymmetrical rectifing etc.
    Good effect, easy to do, lots of circuits.
    All those methods don't affect frequency stability.
    
A2.: One could also directly influence the time constants of an osc,
    this is generally called phase modulation. 
    I think that all extra influences on the time constants of an 
    analog audio osc should be avoided,
    it is allready hard enough to get these damned things stable and 
    I don't want to mess the circuit up with additional leakage or tempcos 
    or offset etc.
    Keep the osc straight and simple is therefore my motto.
    But one could apply ac FM of course, or even self modulation, be it linear or
    exponential. 
    (Better use TG77 or SY99 for FM or Phase Mod, they are of course stable).
    EMS had the feature of an tri osc with shape regulation up to an slow
    sawtooth, but as I said, at the expense of stability, I think.
    And after all, this sounds pretty much like filtering a tri with a LP filter.
    No revelation, not worth the pain.

Digital : Everything you want, but this is of topic here ;>.
    

m.c.