MOTM

But would you really want velocity to simply control sustain level? It's
easiest to implement electronically, sure, and nice & neat on the front
panel, but is it the best way to create envelopes? This wouldn't simulate
the way energy is introduced & dissipated in natural systems. That's all I'm
saying.

Lets say you whack "something" with a mallet.

Now let's say you whack it harder.

Using the simplified "Ussachevsky-esque" ADSR metrics of the envelope, what
has happened on the second strike isn't just a rise in the sustain level. As
far as the ear is concerned, that's the least of it.

What typically happens (and this is a gross generalization of course, and of
a percussive sound per the example) is that the attack is faster, the attack
peak is higher, decay rate is sharper, the ratio between the overall peak
and sustain level actually *increases* (even though all levels are higher),
and the length of time it takes for the steady-state energy to dissipate is
longer, but it does eventually dissipate.

(In addition, chaotic frequecy modulation is increased in the attack, etc.,
but we're just talking amplitude envelopes here.)

Only in a system (such as a pipe organ) where energy is continually fed into
the system does the sustain level remain somewhat constant. For this, the
standard ADSR is perfect. Which is why, as has been said, most synthesizer
work tends to degenerate into quasi-organ character.

(The excellent UEG, as mentioned, is great for complex envelopes, but the
stages aren't VC-able, which is why I hadn't mentioned it in this outing.)

The way the typical synthesizer patch simulates the above is to use two EGs,
and while the VCA EG's sustain is holding firm, an EG controlling the Fc of
a VCLPF is using a long Decay stage to slowly filter more & more high
frequency content away during the envelope's Sustain portion.
Psychoacoustically, this roughly simulates (for a while) energy being
dissipated in a natural system, but it's a real finger-painting approach
compared to actually simulating the amplitude envelope properly.

If you just want velocity data to control loudness in a simple way, than the
easy thing to do is to set up a simple ADSR for the rough characteristic
envelope and then feed the final sound through a VC AR for final amplitude
shaping. And add that VCF EG too. This takes care of the initial velocity CV
of which you speak.

Anyway, this is all just waxing poetic. In the world of synthesizers, VC
envelope control is a strange rarity. *Anything* is an improvement, so I'm
just thinking out loud about these variations. The amplitude envelope is the
single most distinguishing charteristic of a sound, yet most of us spend
more time thinking about VCOs & VCFs. This is why a Korg MS-10 does a
simple, but decent (for what it is) job imitating natural sounds! (And I'm
not besmirching VCOs... I happen to be a VCO-head, myself.)

But envelopes are everything!

Sorry, I just love envelope generators. You just cannot have too many.

OT: has everyone been watching the "April Fool's Weekend" Monty Python
festival on BBC America? That's why I'm a bit punchy right now. DST folks,
don't forget to set your clocks ahead.


 

-----Original Message-----
From: elhardt@...
To: motm@yahoogroups.com
Sent: 3/31/01 8:14 PM
Subject: Re: [motm] Super VC DADSR EG

jwbarlow@... writes:

>>I have to admit, I find this idea much more interesting than a basic
VC 
sustain level (since I can see little use for increasing the sustain
level 
over time).<<

VC sustain doesn't necessarily mean you are changing its level over
time.  It 
could mean you are giving it an initial control voltage everytime you
strike 
a key.  Keyboard velocity could determine its level every note, or a key

triggered S/H for a random sustain level every note.  I'd hate to see it
get 
too confusing or move too far away from what a VC-DADSR is supposed to
be 
with it replacing sustain with "leakage".  There is always the UEG for
more 
complex decay curves.

-Elhardt