The PRK adds a velocity-sensitive weighted 6-octave keyboard to the PPG System.
Als a real child of its time, the PRK has no MIDI; this came with its successor, the PRK-FD. It doesn't have internal sound generation capabilities; its sole purpose is to control the sound generation units (Wave, EVU) of the PPG System.
The device is based on an 6809 processor.
As a special option, up to 7 sound cards can be installed in the PRK that allow to play a range of natural sounds on the attached Waves of type 2.3 and EVUs.
The keys of the PRK are made of wood with a plastic coating and allow a piano-like feeling (and weight :-). Here's a picture of one of the keys:
A "specialty" of these keys, however, is the end part:
There's a plastic angle glued to the wood which has a slot where a spring is inserted that is moved between two contacts when the key is pressed.
In principle, this might be a sound method... but not extremely well crafted, since the glue used to attach the angle seems to lose its power after some years, especially under bad storage conditions. Result: the plastic angles come loose or are drawn into a totally incorrect position by the power of the spring, so that the key can't be played any more. On my PRK, I had to correct and re-glue practically each of the 72 keys.