What does it mean?
Its specific meaning depends on the effect: compressor gain reduction, an Auto Swell fade, a synth envelope, or picking detail in a simulator. It is not always a fixed wait before processing begins.
ExampleA slower compressor attack can let the picking transient stand out.
How the meaning changes between controls
Compressor
How quickly gain reduction follows rising level; a slower attack can preserve the transient.
Auto Swell
The time or speed of the rising fade after the envelope opens it. This differs from compressor attack.
Guitar Synth
Shaping the start of the voice's envelope; certain models use labels such as Percussion or Impact.
Acoustic Simulator
The amount of picking or transient character on a 0–10 control scale; this is an amount, not a time in milliseconds.