voltage processor

This module mixes and can also invert incoming signals. There are 3 sets of paired inputs and 2 outputs, three passive attenuators, and the ability to add a fixed DC offset to the signals on the third set of paired inputs. This is a very useful module because it can mix audio as well as control voltages and can provide inverted and non-inverted versions of the input signal(s).

http://synthcube.com/cart/steiner-ingebretsen-en/synthasystem-voltage-processor-mixer-euro