> Electrically the type of the envelope circuit (loading / unloading a
> capacitor) is completely the same on both modules.

That's correct. But the switchover point (i.e. where the attack ends and the
decay begins) is another parameter which is normally fixed in envelope
generators. If this level is smaller only the lower section of the loading
curve is used for the attack. If it's higher more of the asymptotic share
(where the voltage converges to the max. capacitor value) of the curve is
used. I have considered to add this as an additional parameter to an
envelope generator but then rejected this idea because changing this
parameter also affects the maximal envelope level and the attack time. It's
very difficult to compensate this with analog circuitry.

Best wishes
Dieter Doepfer