The Roland SonicCell answers the question that's been haunting mankind since the first resemblant, hairy biped discovered opposable thumbs and imagined all of the ways to use them on a synth module.
Using EML Polybox, you can make polyphonic sound with 1 VCO monophonic synthesizer. Connection is Korg MS-10(1VCO synth) VCO out (customized) --- Polybox --- MS-10 VCF in