Proteus is a generative sequencer. It creates a melody, then loops that melody for a while, until it gets bored and creates a new one. While it's looping the melody, it may transpose by octave or mutate individual notes as controlled by the knobs or CV.

A video manual can be found here:

https://www.youtube.com/watch?v=87xa5PGlesA&t=19s

The Versio hardware does not allow for CV/Gate out, so instead of putting out v/oct, this version of Proteus makes a full voice. The voice can be switched between a formant oscillator and a Karplus-Strong string voice using the bottom switch.