via this auction
"The Sequential Circuits Prophet VS - Analog-Ddigital Hybrid version of the famous Prophet 5, featuring a vector joystick for controlling sound modeling... [the following appears to be pulled from this Perfect Circuit article]
'Chris Meyer, the conceptual creator of the Prophet VS, states that the "Eureka" moment that led to the Prophet VS emerged from a conversation about the PPG Wave—while drawing an explanation of the Wave's interpolation method, it occurred to him that waveshapes could be interpolated in two dimensions. That is to say—rather than fading constantly between two waves on opposite ends of a spectrum, it could be possible to have a diamond shape with different waves at each corner, and to traverse seamlessly between the four in order to create a wealth of timbral variety from only a handful of distinct shapes. Meyer went on to test his hypothesis on his personal modular synthesizer, using a huge number of resources to manage the two-dimensional crossfading he sought—but his experiment was successful. And though the name did not emerge until later, this is when Vector Synthesis was born.
And while this reduction of the technique may seem straightforward, managing the continuous blending between four sound sources requires a lot of resources: in the analog world, it would require VCAs whose levels change in tandem with one another—an effect that would require tons of offsets, polarizers, and signal multiples (let alone patch cables) in order to work. The genius of the Prophet VS lies not only in its embrace of novel sound design...it also lies in its remarkable vocabulary of modulation sources, and their relationship to the core idea of two-dimensional waveshaping.'"
