Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
The high-pitched whine (which is quite abnormal) and the other symptoms not really sounding like a consequence of settings, altogether hint that the Korg has had an electronics failure. It's 'broken' in some fashion, among the chips that generate and amplify the tones, and will need electronics repair.
Where are you located? I can get you listings for places to take it for repairs.
And, how old is it? if young enough, it might be repaired for free under warranty terms.
Let me know, please. Thanks.