Hi LBH,
As it seems like a bug, this is actually how a 'real' MS-20 envelope behave, here's why:
A second output of EG2 is routed to the filter’s cutoffs by default, unless a patch cable is plugged in via the patch panel.
This second output behaves differently than the amp output, since the sustain level will never be added to the set cutoff frequency.
Raising the sustain level will not raise the filter’s cutoff as one might expect.
Instead, it moves the envelope below the cutoff frequency by the amount of the sustain level.
This is only audible during the attack and release phases.
In case both are set to their leftmost position, it is not audible.
Raising the sustain level reduces the headroom for the decay, just as it does on a common ADSR envelope.
Reducing the sustain level does not lower the cutoff. However, since it closes the amplifier, the sound will lose volume.
Let me know if that's clear enough
![Cheesy :D](http://forum.arturia.com/Smileys/classic/cheesy.gif)
Thanks
Adrien
QA Technician - ARTURIA