The Model D’s keyboard generates velocity and aftertouch CVs. These aren’t connected internally so, unless you insert cables into the velocity and aftertouch outputs on the rear panel and route them somewhere sensible, nothing will happen. On the Minimoog itself, you can choose from the four CV inputs — loudness, brightness, pitch and modulation source as destinations for your VELOCITY Control Output.
Connect a 1/4” TS to 1/4” TS instrument cable from the VELOCITY Control Output to the LOUDNESS Ext. Control Input. Now, the velocity with which a note is played will affect the Loudness, or output volume of the Model D. Use the adjustable trimpot adjacent to the VELOCITY INT. Control Output to determine the amount of velocity control.