He may not look it, in a spiffy double-breasted suit and a coiffure secured with enough hair gel to reflect the ceiling lights, but the 45-year-old music executive confides a secret as he rubs his temples: He’s hung over.

But he doesn’t mind nursing this headache, at well past 2 p.m. on a Thursday in Seoul. Some of his best songwriting ideas come to him, he said, in the malaise that follows a night of hard drinking.

The man doing the creative suffering is Psy, a onetime global internet sensation whose 2012 viral music video and earworm of a song, "Gangnam Style,” became the first YouTube offering to surpass 1 billion views and had the world galloping along with him.