Envelopes control the shape of a sound depending on which parameter they are applied to. Common envelopes contained within a synthesizer include but are certainly not limited to, amplitude, LFO, filter and pitch. Often, the envelope of a particular parameter may be mapped to another destination allowing multiple parameters to move via the same envelope.
The amplitude envelope is the most important envelop as it determines the sonic map and presence of a sound.
This particular envelope simulates a standard synth lead amplitude envelope. Initial punch with the attack and decay creating an amplitude spike while the sustain level holds a little lower generating the character and tone of a wave-shape.
For articulation, definition and impact;
Adjust the attack and decay times
For strength, loudness and emphasis;
Adjust the sustain level
For size, resonance and material;
Adjust the release time
The amplitude is by far the most important part of a sounds movement as it allows the effect of other envelopes to exist. Ensure that your amplitude envelope times and values exceed that of your other envelopes or else modulation shall be interrupted. Unless this is a desired effect, be sure to pay attention to envelope times.
Pitch Envelope
The pitch envelope is the second greatest influencer of a sound as it determines where a sound resides in the frequency spectrum.
This particular envelope simulates a pitch sweep down from an initially high frequency.
Pitch down envelopes can be used for instruments that simulate the tone of a resonating body, such as a drum, string, tube or membrane.
Pitch up envelopes are used for specific sounds such as water droplets.
Filter Envelope
The filter envelope merely influences, rather than change, the character and depth of a sound by altering frequency content.
This particular envelope simulates a climb and drop in position of the frequency cutoff of a low pass filter shape.
Effective filter modulation can be applied by referencing frequencies and their relative feeling and character.
Low frequencies determine size and power, rolling off the low end of the spectrum will distance a sound from the listener reducing its relative size and removing power.
High frequencies contain articulation and definition, rolling off the high end creates muffled sounds and removes clarity and direction.
LFO Envelope
The LFO envelope is a relatively unique type of modulation.
Not only can an LFO modulate a parameter in pre-determined cycles over and over again, the envelope now allows an LFO to begin, hold and continue modulation depending on the parameters set on the envelope.
This particular shape simulates a gradual increase of LFO modulation, maximum modulation throughout the duration of a sustained note and a gradual modulation drop off after the note is released.
As you become more familiar with mixing, mastering, sound design and the music production process, you will begin to understand the importance of accurate envelopes!
For more information regarding envelopes, refer to Digital Audio Tips #008 ADSR and Transients, click image!