BMC10. DDN "Tone and Noise" Firmware
These are 8-bit digital percussion modules. Input a trigger or gate signal to the input and you get either decaying digital noise or a decaying square wave from the output jack. Each channel has one knob which controls either the decay rate or the frequency of the tone/noise depending on how you have a switch set. The CV input allows you to use external control voltages over the decay or frequency and the knob for that channel would attenuate this control voltage.
Here's a mumbly youtube video demo of this module.
WIDTH = 6HP
DEPTH = 55MM
POSITIVE CURRENT DRAW = 8ma
NEGATIVE CURRENT DRAW = 7ma
PRICE = $80
There are currently 5 available.
You could definitely build this module yourself. PCB/PICs are available for DIYers.