Rod Stewart on His Hair and That Nasty Rumor

Rod Stewart on His Hair and That Nasty Rumor (ABC News)

By Juju Chang and Chris Murphey:

Rod Stewart is no longer a young Turk, but he's still selling out shows with his raspy voice, just as he did back in the '80s after he took that detour to disco. Who could forget "Da Ya Think I'm Sexy?"

But it's Stewart as a crooner taking on the American songbook that's catapulted him into becoming one of the best-selling musicians of all time - and a headliner at Caesars Palace.

Watch the full story on "Nightline" tonight at 11:35 p.m. ET

So what's propelled Stewart through five decades of success? He says he is a man driven by his many obsessions.

Take that famous head of hair, for instance.

"There's good days and there's bad days, and it's been like this off and on for 40-odd years," he said.

How did he first get the look?

"Those were the days before hair lacquer," Stewart said. "Sugar and warm water, and rub it in there. And then it sticks up, erect, you know."