RickWartzok built this thing from a block diagram by 
WardCunningham.
It used an analog four quadrant multiplier and 
other AnalogStuff that has faded from memory.
It was suppose to display an orb that wiggled and pulsed
with the average volume level on each of the four channels
of a quadraphonic recording.  The goal was a display that
was more ergonomic than four VU meters in a row.

It was never put into service.  But it did draw some
pretty incredible pictures in prototype form. 
The best images came from an fm stereo when tuned to 
interstation noise.