[sdiy] Question about Envelopes

[Chromatest J. Pantsmaker]

To be clear, I think she understands what an EG *does*, just not *why* it's
called that.

To Ben's point, I think it would still be an Envelope Generator which
controls the VCF, if you think of the timbre as a property which has to
remain inside the envelope.

I think the best answer was Stephan, but only when clarified by Gordon.

Michael's answer was enlightening as well.

Chris ran into the same problem that I did initially, finding answers to
the wrong question.  ;-)

The answers that say it comes from AM radio days just create a new
question, why is *that* called an envelope.  I think Stephan, Gordon and
probably Michael answer that question.

Thanks everybody!

-chromatest


On Thu, Nov 30, 2017 at 1:23 PM, Ben Bradley <ben.pi.bradley at gmail.com>
wrote:

> >Yes, I think 'envelope' in synth jargon comes from the envelope in the
> term 'modulation envelope' from AM radio engineering.
>
> Yes, I think this is the origin (not that it does a whole lot to
> explain synth envelopes). A phrase I've heard in amateur radio is
> "peak envelope power" for a modulated signal (whether AM or Single
> Sidebamd), the peak power of the RF.
>
> But the thing is an ADSR/EG does NOT generate an envelope by itself,
> it only generates a control voltage! Its CV output controlling a VCA
> with an audio signal through it generates an envelope.
>
> The way I'd describe its use is in regards to attack, sustain and
> decay of different instruments. Guitar and piano notes get to full
> volume instantly, then slowly fade away.  Violin, horn and pipe organ
> tones have a slower attack and build up over a fraction of a second,
> then sustain as long as the player can keep it going. The ADSR
> controlling a VCA lets you emulate/simulate these things, at least the
> volume portion of the sound.
>
> The timbre also changes with time, and that can be simulated with
> another 'envelope' generator controlling a voltage controlled filter,
> but for that one I suppose it might be called something different than
> an envelope. I've seen the word contour used, but perhaps it could be
> called a "dynamic timbre generator."
>
> Also, I promise never to complain about 'reply-all' again, regardless
> of how many times I make the mistake...
>
>
> On Thu, Nov 30, 2017 at 4:21 AM, Gordonjcp <gordonjcp at gjcp.net> wrote:
> > On Wed, Nov 29, 2017 at 09:41:51PM -0800, Stephan Vladimir Bugaj wrote:
> >> It comes from mathematical physics and the concept of the enveloping
> >> curves that tangent the inflection points / outline the extremes of
> >> the signal.
> >
> > This, exactly.  The word "envelope" in this context describes the area
> > enclosed by a curve.  Think in terms of "performance envelope" used in
> > (for example) aircraft dynamics, where you'd draw a patch on a graph of
> > speed versus altitude that describes the maximum and minimum airspeed
> > possible at different air pressures.
> >
> > It comes from the French word "enveloppe", which was a verb meaning to
> > wrap or cover something, from which we get the noun form meaning a thing
> > you wrap or cover something with.
> >
> > --
> > Gordonjcp
> >
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