Korg MONOTRON-DUO Analogue Ribbon SynthesizerFEATURES Korg's monotron DUO analog synthesizer is part of Korg's immensely popular mono line of pint sized analog synths they sound huge yet fit in your pocket. The no frills design gives you two voltage controlled oscillators (hence the name DUO) and the same voltage controller filter circuit from the revered Korg MS10 and MS20 synths. You get the thick, syrupy sound only possible with an analog circuit with the Korg monotron DUO. The real secret