The Oberheim Two Voice was the first Polyphonic Synth designed for musicians. It first appeared in 1974. It had no memory and was quiet a limited Synth.
The Oberheim Two Voice is an analog music synthesizer that was produced from 1975 to 1979 by Oberheim Electronics. The two-voice pro was Oberheim's first compact, programmable and polyphonic synthesizer. This was achieved by coupling two SEM (Synthesizer expansion module) modules and each voice had to be individually programmed and also had its own filter. It was soon superseded by the likes of OSCar, ARP Odyssey and Roland SH-101./
In a reddit AMA on March 31st, 2015, Liam Howlett was asked, "Hi Master, is there any synth/gear you are addicted in?", to which he replied, "i rock analogue keyboards ,, oberheim 2 voice , arp 2600"