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10. THE ENVELOPES
The
envelope
is a fundamental modulation source, perhaps the most important one there
is. Without envelope control, a synthesizer's notes would just drone without stopping, or
simply turn on at full volume when a key was pressed and cut off the moment the key was
released. Not all that interesting (with apologies to pipe organ players).
Envelopes allow events like notes to have a distinct shape, letting them imitate a wide
variety of acoustic instruments as well as sounds only possible on a synthesizer. The
MiniFreak offers two envelopes: one is simply called the Envelope, and the other is the
Cycling Envelope. These two envelopes have similarities, but are defined by very different
modes of operation.
10.1. Envelope stages
10.1.1. Envelope stages: ADSR
The way an envelope changes over time is described by sections called
stages
. While there
are many different ways to define an envelope, the vast majority of synths uses envelopes
made up of a few basic stages.
The most common envelope is the
ADSR
, so named for its four stages:
•
Attack
, which starts when a note is played, and runs from the start of the
envelope (usually 0) up to the maximum value;
•
Decay
, which drops from the maximum value to the sustain value;
•
Sustain
, a value that holds steady for as long as a note is held down;
•
Release
, which drops from the sustain value back down to 0 when the note is no
longer pressed.
Note that the attack, decay, and release are all time values, but the sustain is a level.
The attack time differentiates between the sharp onset of a drum hit or string pluck and the
rising volume of a bowed string or timpani roll. Decay time determines how percussive the
initial part of a sound is when compared to the sustain level, and release time simulates
how long an instrument resonates after it's no longer being excited.
10.1.2. Envelope stages: other types
Some envelopes are designed for simpler uses. For percussive sounds played with a short
trigger pulse, an
AR
envelope is enough to describe the shape of the "hit". However, AR
envelopes are a bit limited, and if you need one, it's easy to create that behavior with a
slightly more complex (and much more useful) envelope.
An
AHR
envelope has three stages: attack and release, with a stage called
Hold
between
them. The Hold setting is a time, not a level; during the Hold time, the envelope stays at
maximum. (An AR envelope is just an AHR with zero Hold time.)
We use the terms
Rise
and
Fall
for the Cycling Envelope... making it an
RHF
envelope. This
terminology is chosen so that when you talk about "attack" vs. "rise" or "release" vs. "fall", it's
obvious which envelope you're referring to.
65 Arturia - User Manual MiniFreak - The Envelopes
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