It's every K.K. Slider song overlapped into a hellish stew. The YouTuber who put up this video says "This is what you hear when the world ends." Kotaku's take is a little more entertaining:
Watch As K.K. Slider Sings Open the Gates of Hell
What's happening here is damaging to eyes, ears and souls alike, and also most likely totally NSFW. Unless you want a portal to the 7th level of Hades to tear itself open beneath your office's floorboards, dragging all and sundry to the fiery, eternal depths below. In that case, knock yourself out.