If you want to protect it from spikes you have to use a cap.
The korg you're referring to, is monotron/monotribe/volca ? They send 5v pulses, but who knows? The best way
is to use 2 diodes, a cap and a resistor. Check it on grumpy mike's page.
Anyways i'm not sure what you're trying to do. But i suppose you're making a sequencer and sync it to korg master analog clock...
Then you want to send midi clock messages with the tempo of the korg clock? Just remember one thing, midi clock is 24ppqn. And the analog clock generally is 1ppqn