On envelopes

[KEVIN AUSTIN <KAUSTIN@xxxxxxxxxxxxxxxxx>]

Massimo wrote:

>Subject: Re: Perceived duration of attack and decay

>What I mean with attack transient is the first part of a musical sound
>(from zero to the maximum intensity), and with decay transient the last
>part of a musical sound (from maximum intensity to the zero
>intensity).

>Also, if you produce a musical sound with an attack and a decay
>(i.e. both of 2 sec. of duration), without the sustain period
>you can compare the perceived duration of the two parts (attack
>and decay).


In reply to Jen's

>>I know several that relate to compared perception of duration, but I'm not
>>sure what you mean by duration of attack and decay.  Might you clarify a bit?


In the realm of modular analog (electronic music) synthesis, this
question (and the reply) is a little more complex. The generic control
module for this is called an ADSR (Attack [t], Decay [t], Sustain [l],
Release [t], where [t] = time and [l] = level). (Also called an "envelope
generator" [EG].)

One of the earliest of these (built by Hugh Le Caine in the 50s) was a two
stage AD, connected to a VCA. (He had designed and built VCFs, but the EG
did not control it.) The British company EMS built a (non-standard) ASRO
(Attack - Sustain - Release - Off) envelope generator in the late 60s, at
the same time that Moog was building and ASR, and ADSR module.

Other companies built some EGs with more stages, with _many_ more knobs.
Digital (modular) synthesis allows for the creation of any 'envelope shape'.


With modular ea, this envelope could be applied to any of the (then) three
parameters (amplitude, spectrum, freqeuncy) of an electronic music
synthesized sound. This allowed the spectrum to have one (or more)
envelope(s), and the amplitude to have another. Subsequent developments
have shown that (in musical [sic] sounds), partials have their own
envelopes, most often much more complex than a simple two- three- or
four-stage description.


The two basic types of (musical) envelopes 'transient' and 'sustained',
are differentiated by whether the energy source is of a transient
(occuring once) nature, eg piano, gong, pizzicato, or a continuing nature
(air, bow, electricity).

I believe that the original question refers to transient envelopes, and
only examining the amplitude characteristics.



Best

Kevin
kaustin@vax2.concordia.ca



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