Don't know if this new version works the same way, but the original UniVibe wasn't a true chorus pedal--it was one of the earliest phasers. It had a vibrato mode and a chorus mode, though the latter is what most people consider its characteristic sound. There's a detailed description of how phasers work HERE at R.G. Keen's excellent Geofex website. When the phase-shifted "wet" signal is mixed back with the dry signal, you hear the "chorus" effect. If just the wet signal is passed along, then as the delay is modulated--the pedal's "sweep"--the frequency shifts up and down, giving the vibrato effect.