Doof is a drum module. The design is typical of early 80s drum modules, best to look at the schematic to grok it. In this design, the VCO is a trimmed down version from the NLC dual OTA VCO and the VCA is the same as the ones in the NLC Matrix Mixer.
CV decay (on version 5)
Link to Mouser Cart (1st vers): http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=219310BBC5
Replace the 10nF cap with a link for 808 style gate driven drum hits (Steve's suggestion!)
Techniques for using this module
Post links to videos or audio showing use, either alone or in featured in patches