Hi Ingo

> the simplest example is stereo panning.
> one channel opens with a positive voltage while the
> opposite channel is closed by the same, but inverted
> voltage.

Sorry, but panning requires no negative voltages. The VCA should close
completely with +/- 0 Volt.

A better example for the use of negative voltages on a VCA is a compressor:
The Audiosignal is fed to the VCA (A130) and parallel to the external
input/envelope follower (A119).
The gain cv of the VCA should be set to +5 Volt, so the audio signal can
pass the VCA 1:1.
The output voltage of the Env Follower is inverted and used as CV2 for
the VCA.
The amount of the CV2 controlls the ratio of compression.

Florian