30 years later...
gstopp at fibermux.com
gstopp at fibermux.com
Thu Oct 31 19:15:14 CET 1996
Four waveforms in thiry years... there's a reason for that! The
triangle, sine, saw, and rectangular cover almost all of the harmonic
content requirements - no others are really needed. The electronic
function generator provides these waveforms easily, so that's why they
are what they are.
See here's the deal - if you draw a waveform, any waveform, some
squiggle, with curves and slopes and whatever, and define a start
point and an end point, and then oscillate it, it will probably sound
just like one of the four waveforms above or a simple combination of
them. If the same wave repeats over and over again, it is a static
sound. It can be buzzy or dull or thin or full, but it will be a
To be interesting it must move. It must change in subtle ways from
cycle to cycle in order to be an improvement on the four basic
waveforms. Pulse width modulation, beating VCO's, and animation will
make things more sonically interesting. So will wavetable scanning.
Using a sequencer as a waveform "graph" will give you some nice buzzy
yet boring waves, but if you try this also try moving the pots while
you listen and you will hear the animation.
Shift registers and low-resolution wavetable scanners sound very
gratchety and machine-like because there's a lot of higher frequency
"sub-waveforms" inside the main waveform. These are actually pretty
cool and I think I should try to experiment in that direction some
day! PPG owners already know this stuff. I heard a Digisound EPROM
scanning VCO over at Kevin Lightner's a while back, and it was pretty
I like the "backwards" waveform idea. You'd need to modulate time
itself for that trick, maybe in a few years? Make it
______________________________ Reply Separator _________________________________
Subject: Re: 30 years later...
Author: Christopher_List at Sonymusic.Com at ccrelayout
Date: 10/31/96 10:39 AM
Let's not forget the various "pseudo-digital" waveforms that you can do
1. Stepping a sequencer at audio frequency. A four or eight step
sequencer, with one or two rows, dedicated to a task like this (i.e. no
internal clock, no up / down, etc) would be super easy to build -
basically just some pots, a 4017, and an op-amp or two...
2. Stepping through eprom values using a VCO'd square wave and a counter.
This guantees the waveshape will always be the same.
3. Scott Gravenhorst's "Complex Waveform Generator" that uses XOR
While the PPG and ProphetVS use method 2 - as far as I know, they do it
digitally, not using a VCO to drive the circuit. Therefore, it's safe to
say that if you're looking for any of these methods in an actual
production synth, you won't find them.
More stuff to think about;
I always thought it would be cool to stack up four VCOs and have them
hardwired to be at different intervals relative to one another and have
volume settings for each one - so that you could have instant partials.
There'd only be one set of controls for all the VCO's, and there'd be one
set of the usual sine/tri/saw/pulse outs. The cost in MAT-03s would make
this one expensive VCO!
As I mentioned a while ago, a great method of getting new wave shapes is
to use a VCO (at audio frequency) to;
1. X-fade between two other VCOs (or a VCO and the same VCO filtered)
2. Control the CV on "Timbre Modulator #2" - the full wave-rectifying
Lastly, it would be really easy to build some kind of x-fade or flip-flop
or counter into your VCO so that you had an output wave form that came
out as half square then half saw then half tri or some combination of the
above (which I guess is what you want - everything done at the VCO level
- no other circuits). Though this would color the sound, but I don't
think it would change it too drasticly.
What sort of a waveform would you like to see - outside of a sample? Take
the Waldorf uWave - they put all kinds of different waves in there - but
most of them sound very similar (or the same) - until you filter them or
mix them - so why bother?
ps - what I'd like to see is a wave form that goes <backwards>
- so it would look like this on the scope;
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