well a couple of points:
the a-138m can be used for both cv and audio
if you want to use one (or I think more) of the channels as DC offsets - then you need to set the jumper on the back... if you then use jumpered channels with inputs then the normalisation of the dc-offset is broken and the input is used...
what can you use matrix mixers for:
taking n signals and getting n different signals out - this is particularly useful for:
mixing and routing audio signals to different outputs (ie effects/filters etc) - parallel processing/4 different mixed waveforms from a single vco etc etc
combining and routing modulation inputs to produce more complex modulation outputs - possibly including dc-offsets
adding send/return to mixers that don't have send/return - for example send stereo input (channels 1 & 2) to effects module and then return that to (channels 3 & 4) and then mix channels 1/3 & 2/4 to get a wet/dry mix on the channel 3 & 4 outputs)
take n sequences and mix them together to make n different sequences - basically the same as point 2 - feed into quantizers to keep everything in tune - use the offset perhaps to change octaves or root notes - this will also work with gates
etc etc etc
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities