A monophonic, analog synth prototyped by Octave-Plateau during the development of the Voyetra 8. It used the same voice architecture as the 8. It had more front-panel controls than the 8 did, and would have served as a programmer for the 8 (which badly needed one), in addition to being a synth itself. It also had a built-in sequencer, which could drive not only the One itself, but an attached 8 via the VPK keyboard bus.
The Voyetra One and Voyetra 8 were envisioned by Octave-Plateau as the first two elements of a system (as can be see in the advertisement reproduced below). However, the Voyetra One never went into production, for reasons that remain unclear. Octave-Plateau turned away from hardware development after the release of the Voyetra 8, so whatever other elements were envisioned for a Voyetra family of products never emerged.
Shown below is a Voyetra magazine ad from 1983. The Voyetra One is pictured at the top, with the 8 at the bottom, and the VPK-5 keyboard (which played either synth) in between.