This 12HP Envelope Generator gives you four separate Attack Release Evelopes. Each of these can be triggered using the 'gate' input and outputs the envelope via the 'out' output. The Attack knob can be used to control the speed at which the envelope's signal rises. The release knob on other hand control the speed at which the signal decreases. The envelope can be used to control anything that is voltage controlable, like for instance the threshold of a filter, or the amplification of a VCA. Both the Attack and Release can be extremely short (i.e. instant) or multiple seconds long. The fact that this module does not have just one or two envelope generators can come in very handy. I usually use it to control multiple different modules that alter a certain sound. For example, the module can control both a VCA, VCF and Wave Folder that all alter the same sound. As all envelopes can have different Attack and Release speeds, this can create multiple layers of interesting changes that happen to the sound.