The Realizer was the last machine PPG (Palm Products GmbH) produced. In fact very few were finished or released so it's pretty rare. The Realizer was very unique in its effort to combine sound production, emulation, processing, recording, sequencing, and mixing into one all-digital system. A concept that was very much ahead of its time considering that we're only now seeing affordable software-based devices that can offer this type of environment.
As for synthesizing sounds, the Realizer features an analog model, an FM model, wavetable synthesis, and a sampler. They were designed to show an image of a Minimoog, or other synth on their built-in monitor. Then you could control the Minimoog knobs with the controls around the screen of the Realizer. Pretty space-age stuff for 1986! Unfortunately, the price tag of $65,000 didn't exactly make it a marketer's dream. It was the last thing that PPG made, and they went out of business a short time later.
Thanks to Roger Cordell at Big City Music for providing some information and the original image.