Couple of things to set straight first … the MS20 has its own way of doing things and that’s what makes it so very special imho (besides the glorious sounding voice) So conventional thinking if you’re used to more popular synth paradigms will get you stuck a bit; things like the Hz/v tuning, the modulation of the amp envelope and a few other things, including the ‘Sample and Hold’ - I’ve read it described as more of a ‘track and hold’ i.e. the input is always followed when open and the snapshot is taken when closed(held)
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Now another idiosyncrasy of the MS20 is the ability to use grounding to trigger things (see screen print under the ‘passive’ button) - this means you can wire up an external push to close switch and ‘ground’ the action (as opposed to sending an active ‘high’ voltage to trigger things, this has advantages)
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So to do this with the A4 you need to know that the Korg will pull to ground when you send a voltage that is lower than approx 1.3v - you can test this by setting a CV channel up as value lin, make the range be 0v to 1.5v and vary the value whilst connected to the S&H ‘clock’ (hook a slow ramp lfo to the input and put the output on the pitch) … you should see that when the voltage is high (i.e. value lin is at 127 that the ‘track and hold’ will pass the lfo through, but if you drop the value lin down to 100 or so, it’ll drop the voltage sufficiently to effectively ground the circuit (& then hold).
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So you need to be able to drop a voltage beneath a 1.3ish threshold to act as a ‘clock’ in your case, now if you want a typical ‘S&H’ effect where the effect is steps, then all you need to do is set up e.g. an envelope which is targeting the value lin value (set it to zero on its main twiddle page (ie 0-127)) if you set all parameters of the Env to zero then you get a very fast voltage spike which momentarily exceeds 1.3v and allows the input through, but because it is so fast the ‘tracking’ isn’t heard, you just get the stepping effect whenever you play a key
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So that’s how to get it going, to make it work best for yourself you’ll want to use any number of strategies to work the voltages - if you don’t want it linked to keyboard action you have lots of options to explore - remember that the MS20 noise section is quite low voltage, so as a mod source it’s underpowered, you’re best using the ramp LFO set fast to get a broader ‘random’ input to sample - the CV potential of the A4 is extremely powerful, so you ought to be able to get what you’re after with a bit of thought
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