Korg uses osillators[sound sources] to make a voice[patch/tone]..Most of the better sounds on the Korg are two osillator [composite]tones..
If you play a two osillator tone, you are actually using 2 polyphony for each key you press,yielding half of the maxinum polyphony[31]..
You can see how important it is to have good voice allocation[voice priority]. Especially playing full arrangement[style], or sequences played with a live part..