The Mono/Poly was first released in 1981 and was available at the same time as the Korg PolySix. It is a 4-voice polyphonic synthesizer with 4 independent voltage-controlled oscillators that can generate sine, sawtooth, pulse width, and pulse width modulation waveforms. These oscillators can also be used in unison for a monophonic lead tone - thus the name Mono/Poly. It also has separate envelope generators for the oscillators and the filter. It has two low-frequency oscillators that can be used to modulate the envelope, arpeggiator, and pulse width independently.
It uses SSM2033 chips for its VCOs and an SSM2044 chip for its filters.
The Mono/Poly is known to have been used by 808 State, Chemical Brothers, Hardfloor, Juno Reactor, Tangerine Dream, and The Orb.