The A-191 is a combination of a MIDI-CV interface and a Shepard Generator. Most of the controls, indicators and in/outputs have a double function; there is a switch which toggles between the two sets of functions. In use as a MIDI-CV interface, 13 of the 16 control voltage outputs are dedicated to sending voltages converted from a particular MIDI controller (such as Mod Wheel, Volume, Pitch Wheel, Aftertouch, etc.). Controller messages on the chosen MIDI channel are converted into voltages in a range from 0 to 5 V. The other three sockets output an internal LFO generated in sync with MIDI clock, in three waveforms: sawtooth, triangle and rectangle.
In use as a Shepard Generator, the sockets output eight different phases each of a triangle and sawtooth wave. The Shepard Generator creates in combination with other modules (VCO's, VCF's, VCP's, VCA's, Mixers) psycho-acoustic so-called Barberpole effects like never ending rising (or falling) phasings (with VCPs), filterings (with VCF's) or tones (with VCOs). To create the Barberpole effect you need the required additional modules in your system. For a good Barberpole effect it is recommended a minimum of 4 VCP's (or VCF's or VCO's) and 4 VCA's (linear types). With 8 modules instead of 4 the sound becomes more smooth and tight.
All A-191 settings can be saved into non-volatile memory.