Sines includes four almost-identical envelope generators:dedicated envelopes for the Filter and Amplifier, and two auxiliary envelope generators (Envelope 3 and 4) usable as mod sources for many Sines mod destinations. The dedicated Filter envelope generator is hardwired to the the filter Cutoff control, and the Amp Env is hardwired to Sines' onboard VCA for overall amplitude shaping.
Here's an overview of how Sines' envelope generators works:
When a note is played, the envelope generator outputs a dynamically changing voltage, according to the settings of its four stages. The delay stages waits for the set duration, then the attack stage defines how long it takes for the output voltage to rise to maximum. Once the attack stage reaches maximum amount, it moves to the decay phase, which defines how long it takes to fall from maximum to the setting of the sustain phase. Unlike the delay, attack, decay, and release phases, which define times, sustain simply sets the held voltage following the attack and decay phases - this equates to the envelope output level while holding down a key. Finally, the release slider defines the length of time it takes for amplitude to fall back to zero when the gate input voltage is removed, i.e. when the key is released.
Delay- Defines the length of time prior to the start of the attack phase.
Velocity- Defines how much the envelope affects the filter cutoff frequency via keyboard velocity. When set to zero, keyboard velocity has no effect on cutoff frequency. Seting the knob clockwise from center increases the envelope output voltage as keys are struck harder, setting the knob counterclockwise from center decreases the envelope output voltage as keys are struck harder.
Attack- Defines the length of time for voltage to rise from silence to max amplitude when a key is played.
Decay- Defines the length of time for voltage to fall from the attack stage maximum to sustain stage setting.
Sustain- Sets the amplitude of held notes level following attack and decay phases.
Release- Defines the length of time for amplitude to fall from sustain level to silence when a key is released.
You may have notice that Sines' Filter, and auxiliary envelopes 3 and 4 include a Delay stage for "pausing" the onset of the envelope generator, but the Amp Env does not. Since the Amp Env acts upon the entire sound, a delay control would delay the entire sound from playing, potentially making Sines feel broken. We couldn't figure out a practical reason why anyone would want this, so we left it out. (That said, given Sines' immense Mod Matrix, there are a number of ways you could make this happen if you really wanted to!)