If you have a 500 Series rack with two empty spaces, you owe it to yourself to try out the Elysia nvelope 500. This stereo / dual-mono module is a must-have-desert-island processor for drums and synths. This Class-A discrete processor is an exceptional equalizer and dynamic shaper that offers frequency-dependent control over the attack and sustain of any audio signal. Lengthen the resonance of a bass drum's low end and shorten up the higher frequency attack to get amazing enveloping that no compressor can do on its own. If you're dealing with a synthesizer that has an amazing sound but not so much control over the envelope, this is the module you need. Spend a little time with this module and you'll wind up using it on all sorts of tracks and will quickly wish you had at least one more.