Universal Midi RetrofitThe retrofit covers a 64 note keyboard range and also has an arp clock synced to midi clock at 1/8 or 1/16 note lengths.
Although designed primarily for the Roland Juno series the design works on most premidi polysynths including: Roland Juno 6/60, SH-101, MC-202, Jupiter 4/6/8, Oberheim OB series, Korg Polysix or 61, Sequential Prophet series. They are completely invisible to the synth and fit internally with only a few switches on the front panel for channel select and the arp sync.
Assembly and installation takes about 3-4 hours, instructions here. The retrofit is only available as a short form kit including the PCB's and a Preprogrammed microcontroller.