Hello Quentin

> They noticed that the colour of sound produced by the 3P was not as full and bright as it was before, being one of her favorite sound sources. Is this possible?

Yes, your friend is right. The technical background it the wrong
parameter dimension for the filter settings.

The original JX3P had an envelope amount fo 128 steps and an additional
switch for the envelope polarity. Murray changed this to an
bidirectional envelope amount: Means 64 steps up/normal and 64 steps
down/inverted. But he forgot to multiply the values given by the
potentiometer with 2 for the effective filter modulation. So the filter
does only open the half of the original amount. As far as I know this
shall be fixed in one of the next releases.

Florian