PWM and sinusoids

[Martin Czech]

> turned up the frequency of the LFO to audio frequencies... it was me that
> was impressed. I couldn't believe the tonal textures that could be attained
> by this arrangement.
> 
A kind of complicated phase/amplitude modulation of the partials.  Some
early synths with PWM could do this, since the lfo had also an audio
range (e.g. my old and now relativly dead Roland Jupiter 4).  Well ,
manufactures have to go for the money, and the average musician (maybe
at those days) was not very well informed about synthesis...  So no use
to add such a feature, marketing says ;-> By the way: If you want the
same sound for all the notes, then the lfo must track the vco, i.e.
another vco. Most commercial synths offer no way to modulate vco1 PWM
with vco2.  Again, money...


Sometimes "cross modulation" was possible (Roland, ELKA), but this
flimsy term refers to mutual frequency modulation of vco1->vco2 and at
the same time vco2->vco1.  Since the meaning of "cross modulation" is
not well defined, it could be that some machines modulate PWM in this
case. I don't know.


m.c.

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