The MST Unity Gain Mixer adds input signals together and combines them for a summed output. For example, if you put in a 1V source and a 3V source, the output will be 4V. It's mainly used for CV, but it can also be used to combine audio signals together.

A unity gain mixer is handy in several ways:
Combining gates and triggers. Plug a few sequencer steps into the unity gain inputs, then run the output to a drum synth, VCA, envelope, etc.
Re-shaping two CV sources with a single envelope.
Combining different wave shapes or LFOs to make crazy sounds.
Controlling the CV of one source with the CV of another source. Just plug the CV out of a sequencer into and an expression pedal / touchable CV out into the unity gain inputs.

Specifications:
Current draw:
+12V: 9mA
-12V: 9mA
Module Depth: 22mm
Width: 6HP