What is this technique called?

[Winston Park]

I can't post links because this is a new account. But the sound im talking about is in a video on Youtube. Search:
[h=1]deadmau5 - Untrust (Lawson Extended Version)[/h]
It starts at 4:35 and ends at 4:45

I followed a tutorial for Massive that did this, but I still don't know what it is.

 

[krushing]

Sounds like he's just automating the decay of the synth's amp envelope.