The british company Kenton is probably the market leader in the area of proper MIDI/CV-converters. Probably every vintage synth can be MIDI retrofitted with a Kenton interface. In addition a series of superb MIDI controller fader boxes has been created some years ago, it is discontinued (since european RoHS) unfortunately. Kenton still shines with excellent products like the MidiStream wireless MIDI system and many more interesting devices,
Link to Kenton