The Oberheim 4 Voice is a polyphonic analogue synthesizer used by Prince. It appears on For You and Prince. It is mentioned in the liner notes to For You. It was also used live by Dr Fink and Gayle Chapman.
Polyphonic synthesizers — those had just started happening. They had the Polymoog, but it had only been out a year, two years tops. They were pricey, and they didn’t do a lot yet. The Oberheim four- or eight-voice SEM — they were called the SEM Module versions, basically equivalent of a Minimoog, which you could only play one note at a time on... He had all this state-of-the-art gear when I went into that audition.
By the time I joined him, my personal setup was just a Minimoog, a Rhodes, a Farfisa VIP 345 with a Leslie speaker cabinet, and a Freeman string synthesizer. At that same time, he had all this gear he bought with money from his record deal, so I integrated what I had with what he had. I got rid of the Freeman and went to an ARP String Ensemble, and the old Oberheim Four-Voices and S.E.M. modules. I kept the Minimoog, and added a [Hohner] Clavinet and an ARP Pro-Soloist... a lot of stuff! It was a Rick Wakeman kind of setup. Then, as time went on, I pared things down, and every year kept updating as things changed.