Both can work completely separately or they can be connected on the underside of the modules via an expander cable (included).

So firstly, the Mutagen is a 6 channel mixer in 12hp.

It has clickless mutes on each of the channels, which can also be engaged (on/off) by cv. 

Each channel also has a 3 position switch to select which of the 3 outputs you wish to use.

Outputs A and C also have a master control.

Secondly, the Hex VCA is a 6 channel vca in 8hp.

As well as individuals outs, it has two sum outputs (- and +) which can be used if a cable is not plugged into the vca's direct out.

A cable (included) can connect each individual VCA output into the respective 6 channels of the Mutagen, giving a 6 channel vca mixer, with mutes, three outputs (and the direct outputs can still be accessed at the same time from the Hex VCA or you could even use the sum outputs at the same time).

In brief, there are a ton of potential signal routing options here.

Both works perfectly and in great condition (aside from some screw rash).

Any questions please ask.