This is a stand-alone programmer for analog synthesizers. It can be used for modified hard-wired synths and was intented to be used for the Minimoog and Arp 2600 at the time when it was developed. It can be used with any analog synthesizer though, and works especially well with modular systems that track CV at 1V/oct.
The programmer is basically a memory box that will recall envelope settings and 3 control voltage settings at various memory locations - much like the memory bank/patch in a Prophet 5, PolySix, or Juno-60. So in other words, you could patch the voltage outputs to any input in a modular synth and recall different settings at the press of a button.
There is an input that you can connect a pedal to in order to advance the patch to the next memory location. The really nice thing about this is that you can step through a series of memory locations with an external clock - and therefore, it makes it into an 8 step sequencer that has different envelope settings for every step! The only problem is that sometimes when you use the same clock for triggering the envelope AND step to the next patch, there is a noticeable burst of sound from the previous patch before all of the voltages and envelopes change to the new settings. You can work around this by using different triggers for the envelope than your patch advance, and step to the next patch just slightly before you trigger the envelope.
The Roland Juno-60 had borrowed the idea of having an input to advance the patches. With the Juno, a clock or trigger will work as well as the foot switch.