Oberheim Four Voice
A big step forward after the initial Oberheim SEM and Two Voice synthesizers came from the bigger and better Four Voice. Four dual-oscillator SEM modules each with its own filters and envelopes are joined together along with a simple analog mixer and 49-note keyboard to give you a polyphonic/polytonal Obie-beast!
This combination gives you eight oscillators and four voices of polyphony because there are basically four discrete mono-synths all connected together. This has its pros and cons. What is cool is that this was a lot of simultaneous voices for the mid-seventies. And the ability to craft a different sound on each voice led to some diverse and complex sounds. However, it also meant you have to program each voice independently. Each voice also has its own independent audio output.
The Polyphonic Synthesizer Programmer, released in 1976 and added to the Four Voice stores 16 patches per voice (all of which can be different). The Four Voice could accommodate an additional four SEMs, making it just like the Eight Voice model which officially appeared in 1977.
Unfortunately the Four Voice was blown out of the competition by the release of the polyphonic Sequential Prophet-5, which offered true polyphony with a single set of sound shaping controls and comprehensive patch memory. The Four Voice has been used by 808 State, Depeche Mode, Styx, Pink Floyd, The Shamen, Gary Wright, Joe Zawinul and John Carpenter.
Demos & Media
Images from Perfect Circuit Audio.
Thanks to Bonnie Goodwin for this information.