This is really DBopII. I built the first one after I destroyed my Korg Minipop in 1985. At the time it was the only way I had to get a beat on my 4 track. When it died I was frantic to get a beat somehow and I remembered a series of articles in my collection of 1979 Radio Electronics by James J. Barbarello on the PerSyn percussion synthesizer.
Initial experiments were promising but I hated the sound of his tone generators. A friend had a Radio Shack beat-box that I thought sounded great so after a little reverse engineering I built generators that worked well enough to start construction. The first version had only kick and snare but four programs instead of two. It was a real mistake not to include a hi-hat and now that analog beat boxes are in again I thought it would be cool to do a updated version.
Related: DIY Synthesizer pages