MOTM

After posting possible ideas for using the (hopefully next) dual vca
module at John Potter's request, he and several others have used the
phrase "cv morphing."  Would someone kindly define "cv morphing"?  I
haven't been able to locate the phrase in books, ... on synthesis that I
have.
Thanks, Jeff

Hey Jeff:

Not sure if "CV Morphing" is a commonly accepted term but the term 
morphing by itself is used fairly commonly in synthesis.  For 
example, you hear it alot in reference to the Yamaha AN1X, Nord, EMU 
Z-Plane filters, etc.

I just meant changing the CV source or destination over time.

For example:

Fade a TRIANGLE into a SQUARE LFO Source into OSC Freq Destination

- or - 

Pan SIN LFO Source from Filt Freq to OSC Freq Destinations

that's the general idea I was getting at and pretty much the examples 
you gave.  Hope that helps clear things up.

See ya.

John

--- In motm@y..., Jeffrey Pontius <jpont@k...> wrote:
> After posting possible ideas for using the (hopefully next) dual vca
> module at John Potter's request, he and several others have used the
> phrase "cv morphing."  Would someone kindly define "cv morphing"?  I
> haven't been able to locate the phrase in books, ... on synthesis 
that I
> have.
> Thanks, Jeff

> After posting possible ideas for using the (hopefully next) dual vca
> module at John Potter's request, he and several others have used the
> phrase "cv morphing."  Would someone kindly define "cv morphing"?  I
> haven't been able to locate the phrase in books, ... on synthesis that I
> have.
> Thanks, Jeff

I've built a "morphing programmer" for my modular some years ago,
and the schematics and description can still be found at:
http://home.t-online.de/home/jhaible/morph.html

The text is a mix of my own description and some explaining words
from Kevin Lightner of Synthfool fame - in fact the page pre-dates my
own homepage activities and was created by Kevin.

(I think the general text is still worth reading, but please do *not* build
the circuit. I would do it quite differently today, and the schematics
there have some pitfalls and errors.)

JH.

Von: Tkacs, Ken <ken.tkacs@...>
> In terms of audio signals, Z-plane filters, etc., the term "morphing" does
> have some merit, but those are more complex, multi-dimensional signals,
not
> simple summations.

There's nothing than weighted summations in a digital filter (;->), but
I know that was not your point.
You are completely right:

> A control voltage is just a level at a particular point
> in time, so it seems strange to refer to a varying CV as 'morphing.' Is an
> EG "morphing" it's output? I guess technically, "morph" just means "form,"
> so one could argue that it does, but it seems odd to apply that term to
such
> a simple process. The whole point of voltage-controlled synthesis is the
> ability to alter voltages in real time, so by that definition, they're
*all*
> morphing.

... but there is more:

You build two different sounds (two patches) in a modular. Now you can
use a dual VCA to crossfade between the two signals. That's crossfading,
not morphing.

You can use one synth engine with everything under voltage control,
and then you can switch between sets of CVs. That's what every synth
with patch storage does. Switching, not morphing.

And finally you can do a crossfade for each and every CV, rather than
simple switching. That means a dual VCA for *each* parameter. I think
there is good reason to call this "morphing".

The difference to crossfading can be a dramatic one, depending on
the way you create the morphing. There is more than one way to do it.
Well, sometimes there is just one obvious way: If Sound #2 has
a different decay time on the filter than Sound #1, you will obviously
change the CV for the Decay Time.
But if Sound #2 has a different VCO waveform and / or pitch, you have
some choices: Gliding the pitch up or down is one option, but surely
not to most unobstrusive one. Alternatively, you can use hard sync
and interpolate the pitch CV, or use two locked (hard sync'ed) VCOs
with different pitch and do a crossfade between the two VCO outputs.
Whatever fits your needs for *your* idea of morphing on that particular
sound.

So I need a dual VCA for each parameter ?! (JH. will be glad, because
his royalties will shoot up (;->) )
It's not that bad. You only need VCAs for parameters that are different
for both patches. The good news is that you can do some stunning
morphing with a rather limited number of parameters. My old
morphing programmer has 6 channels (not all are VCA-based, but that's
a different story), and I rarely used them all. More like 4 or 5, normally.

Of course you can do a lot of other weird stuff with all these CV inputs.
You're perfectly right: That's what a modular system is all about.
This morphing stuff is just a subset of the "total freedom": The special
charm of morphing is that you can change a set of several CVs with
*one* CV in a predefined (pre-patched) way.

It's important that this is possible independently of any time constants.
It's not just "start with sound 1, fade to sound 2" - that would be boring.
You can use a controller (pedal, aftertouch, you name it) and morph
halfway from 1 to 2, then back to 1, then fully to 2, all in realtime.
It's like creating a "Macro" of parameters which resonds to your input
in a way you defined it.

I hope this shed some light rather than adding to the confusion,

JH.