This is a simple to make project that will take 2 audio or CV inputs and allow you to attenuvert the 2 signals plus add or reduce gain. Though it seems to work better with CV rather than Audio.
There is a Difference circuit that will take the signal from A and B and give you some interesting voltage signal patterns, The A&B inputs can be swopped by the switch, The signal also has an inverted output and if no jacks are inserted then the unit is readily connected to the +-Bias of the A&B inputs section.
There is also a Summing circuit that will add A&B together, Again if no jacks are inserted into the Sum-A and Sum-B they are automatically connected to +-Bias A&B. as with the Difference circuit there is also an inverted version available.
both the Difference circuit and Summing circuit have level adjust for the inputs.
This unit is rather large for a Eurorack module and takes up too much HP (horizontal pitch) but I just wanted to make it just to see if it could be useful, Maybe I will make a much smaller version on revision 2.