10.6

714Logic Pro Instruments
Attack, decay, sustain, and release
The oscillogram of a percussive tone shown below illustrates the level rising immediately
to the top of its range and then decaying. If you drew a box around the upper half of the
oscillogram, you could consider it the “envelope” of the sound—an image of the level as a
function of time. The role of the envelope generator is to set the shape of this envelope.
The envelope generator usually features four controls—Attack, Decay, Sustain, and
Release, commonly abbreviated as ADSR.
Envelope controls
• Attack: Sets the time it takes for the signal to rise from an amplitude of 0 to 100% (full
amplitude).
• Decay: Sets the time it takes for the signal to fall from 100% amplitude to the
designated sustain level.
• Sustain: Sets the steady amplitude level produced when a key is held down.
• Release: Sets the time it takes for the sound to decay from the sustain level to an
amplitude of 0 when the key is released.
Note: If a key is released during the attack or decay stage, the sustain phase is usually
skipped. A sustain level of 0 produces a piano-like—or percussive—envelope, with no
continuous steady level, even when a key is held.
Modulation
Modulation overview
Without modulation, sounds tend to be uninteresting and fatiguing to the ear. They also
sound synthetic, rather than natural, in the absence of some type of sonic modulation.
Vibrato is a type of modulation commonly used by orchestral string players to add
animation to their instrument pitch.
To make sounds less static, you can use a range of synthesizer controls to modulate
basic sound parameters. To this end, many synthesizers, including ES1, ES2, and Sampler,
provide a modulation router. Alchemy and Sculpture provide further unique modulation
options.
The router enables you to direct, or route, one or more modulation sources (the parameter
or control that is modulating another parameter) to one or more modulation targets (the
parameter being modulated).