An input into part of the synthesizer that allows that bit to be modulated by another part of the synth. For example there is a control input in the amplifier which controls the level of amplification. If a very slow sine wave (an LFO) is patched into this input then the sound will slowly get louder and quieter. If an LFO was patched into the control input of the oscillator instead, then the sound would go higher and lower in pitch....
MS 50
This was the most modular, most complex, and therefore most expensive of Korg's MS
line. It was designed to be an expander and, therefore, had either Hz/volt or volt/octave
interfaces. The MS-50 was totally modular, in that there was no hard-wire patching at
all. A monophonic synth, the MS-10 had one VCO, two VCFs, two VCAs, a voltage
controlled LFO, two ASDRs (with normal and inverted outputs), pink and white noise, a
signal inverter, multiples, a ring modulator, a voltmeter, sample and hold, and a
headphone socket. It is designed to match the SQ10 analog sequencer.