A Utility Mixer is important for mixing CV Signals, Audio Signals and Inverting signals as seen in this video of the STG Soundlabs .Mix Module.
Here are some common differences between CV Signal Mixers and Audio Signal Mixers
Audio Signals typically alternate between positive (+) and negative (-) signals.
Audio Mixers are often AC (alternating current) coupled to remove any voltage offset.
Voltage Offset is a result of any addition or subtraction to the voltage source from an passing signal.
Audio Mixers have simple level controls that attenuate (reduce the force, effect or value of) the signal.
Attenuators are useful for eliminating unwanted distortion or clipping.
Attenuators typically have a logarithmic curve
Good for power based signal levels
Some mixers have overdrive functionality at louder levels to add "color" to the sound.
CV Signals can alternate between +/- , range from 0/+ or remain steady, unchanging voltages other than 0.
Due to these variables we do not want the CV Signal Mixer to remove any voltage offset.
CV Signal Mixers need to be DC (direct current) Coupled for this reason.
CV Mixers can feature more complex level controls that allow the user to invert, amplify or offset voltage signals.
Inverting the signal results in Voltages swinging in the opposite direction
Attenuverters allow the user to invert and attenuate the signal in one level control.
Amplify the signal with level controls that have a linear response.
Offset Voltage by a specified amount
We hope this table provides a good understanding of the ways one can mix together incoming Audio Signals and CV Signals.
Remember that modular synthesis often combines many ideas and uses into one module, therefore, many mixers can serve the function of an Audio Signal Mixer and CV Signal Mixer as well as providing different modulation options through CV control.
Modular synthesis is a journey and understanding the terminology is very useful to understanding the concepts.