“Attack” refers to the first stage of an envelope generator, which is used to shape the amplitude or other parameters of a sound over time. The attack stage determines how quickly the control voltage (CV) rises from its initial value (usually zero) to its peak value when a note is played or a gate signal is activated.
The attack time, which can typically be adjusted using a knob or parameter control on the synthesizer, influences the onset of the sound. Shorter attack times result in a faster, more immediate onset of the sound, creating a sharp or percussive quality. Longer attack times produce a slower, more gradual increase in amplitude or other parameter, giving the sound a softer, more rounded quality.