Empress Effects Phaser - Manual (Page 6)

The Attack and Release Controls
In submodes 1 through 4, the attack switch determines how quickly
the pedal reacts to an increase in input signal volume.
For example, with submode 2 selected and the attack set to fast, a
sudden increase in volume will increase the phaser rate almost
instantly. With the attack set to slow, it takes much longer for the
speed of the effect to increase.
The release knob controls how quickly the pedal reacts to a
decrease in input signal volume. Set fully counter-clockwise the
release time is the fastest. Set fully clockwise the release time is the
slowest.
A slower release time generally sounds a bit smoother and a faster
release time, more abrupt and jarring.
In submodes 5 and 6, the attack switch sets the speed at which the
parameter moves from its minimum to maximum value. The release
knob sets the speed at which the parameter returns back to its
starting value.