LinPlug Octopus - Manual (Page 61)

Again, the sound is more interesting if it's animated, so we'll use an
envelope to modulate the filter's cutoff frequency.
12. Create a new envelope.
13. Set the type to Cutoff.
14. Assign it to Filter 1 in the Envelope Matrix
15. Edit the envelope to a suitable shape.
Congratulations!
You have successfully created your first Octopus patch. Of course, you've
barely scratched the surface of the Octopus' capabilities. If you're interested
in understanding how the Octopus works in more detail then consult the
appropriate sections of this manual.
Manual 59