Because the original PS-3300's voice panels each used twelve independent "divide-down" oscillators, Korg was able to implement fine-tuning controls for each chromatic scale note (repeating through the octaves). This allows unique custom and just-intonated scale tunings (we'll let Wiki explain just intonation, because they're smart and we're lazy).
In case you're not inclined to learn new ear-bending scales (or strangely super correct ones), we've found the temperament adjust feature is also real handy for minute amounts of detuning, and as such, we've provided some handy shortcuts for doing so.
Temperament Knobs- Each knob tunes the appropriate chromatic scale note up or down by 100 cents (i.e. a half-step). The panel says -5 to +5; we're not sure how Korg arrived at that (that's what all the other bipolar knobs say?), but the popup tooltip will display the correct tuning offset.
Temperament Preset menu (white triangle)- Like the ones at the top of the panel, these are easy to miss, but clicking these displays the a couple of useful temperament-related menus:
Clicking the triangle displays the temperament presets menu, including Equal Tempered, Mean Tone System, Hepatonal System (which is extra hep), and Just Intonation with key signature submenus We regret that the Temperament Preset menu does not contain sharks with lasers in the heads, nor ill-tempered sea bass.
Random and its Subtle and Extreme submenus applies random temperament tuning values. These can be useful for making patches sound more natural - particularly the large orchestral brass sounds PS-3300 excels at.
You can alway return to standard half-step tuning by selecting Equal Tempered.