Korg • MS-50
The Korg MS-50 - modular in design and at the height of the MS-series synthesizers. This keyboard-less expander type module is completely patchable and uses Korg's Hz/V type of CV and Gate for control with other synths like the MS-20. There are lots of knobs and patch points on this one... The MS-50 is still a single VCO monophonic analog beast but offered more patchability and power than any other MS synth. Other features include a ring modulator, voltmeter and sample & hold. It was also designed to complement the SQ-10 sequencer. It has been used by The Chemical Brothers.
The MS-50 tends to be quite expensive due to its rarity (it was released in a fairly small quantity a year after the others in the MS series) but is such a great synth. It has both Hz/v and 1v/oct inputs, so can also be used, for example, with Roland mono synths.
An MS-20/MS-50 combination is, in terms of versatility, the equal of an ARP 2600 and, with the MS combination, you also have the advantage of the ESP.