"When your heart says yes, and your mind says no...."

It is, says Tommy Smothers, "the magical state of Yo."

At the end of his appearances with brother Dick while on tour, Tommy likes to dig out his basic $5 yo-yo, wrap its string around his finger and let it fly.

And the yo-yo phenomenon, which was pallid to the point of disappearing just a few years ago, will link Smothers with the yo-crazed younger set that's agog over Cold Fusion, the Brain and transaxles.

Tom and Dick Smothers are kind of like that yo-yo, bouncing up and down as entertainment -- and political -- trends wax and wane. Their variety show was canceled by CBS at a time when anti-Vietnam sentiments weren't what network brass wanted to defend. They had a brief foray into 1980s television. They took gigs where they were invited, began a now-thriving vineyard in California and kept their wits sharp and their repartee quick.

Now they're hot again, and it's in no small part due to a song by collaborator Mason Williams.

Williams brought them a little ditty about traveling yo-yoers, says Tommy, and he suggested they demonstrate some yo-yo action while they sang. So Tommy unstrapped his guitar, strapped on a yo-yo and tried a few tricks.

He stank.

His word for it, laughing, is "pitiful."

"I was never very good" at the game when he was a child, he admits. When he first took it up again as an adult, things weren't much better. There were lots of whacks on the knuckles. But slowly, slowly, his yo-repertoire built. "A lot of people think I'm really good because no one's seen yo-yos for 15 years," he jokes.

Can't be true. The Smothers Brothers' audiences now are a mix of parents who hark back to 1970s TV and a younger brood who's there for one thing and one thing only:

The love of Yo.

Tommy couldn't be happier about it.

"Kids have to use some eye-hand coordination that's not required for Nintendos and that kind of stuff," he says. Many of those kids, the yo-groupies who visit backstage after performances, can do the two-handed shoot-the-moons and all kinds of tricks that result from high-tech yo-yos that provide a longer "sleep time," when they can do tricks.

Tommy hasn't been tempted by that bright, seductive millennium world of yo. "My basic wooden one does everything I need," he says. "In the world of Yo, I'm about a 12 handicap."

That's not to say this golf fanatic's a complete Luddite.

"When it comes to yo-yos, I'm traditional," he admits, laughing, "but in golf I'll use titanium, I'll use anything they got."

Talking with Tommy from his California home, you're bombarded -- in an easy-going way -- with everything from puppy-training advice ("A kennel for them to sleep in. It works for housetraining. Guaranteed.") to the world history of Yo.

He knows the names of Barney Acres and Harvey Lowe, world champions from decades ago. He knows the next world championship will be held in Hawaii. He knows in what year manufacturer Duncan went bankrupt (1965), who developed the high-tech transaxle (Tom Kuhn, a dentist) and what other ideas were devised by the founder of Duncan Industries, the patron saint of Yo (the parking meter and the Good Humor man, Tommy says).

It's the enthusiasm of a convert.

"I carry the yo-yo with me all the time now," he says.

So like a prophet heading out into a rather welcoming desert, Tommy takes the word of Yo wherever he goes. "We did a three-day show for IBM a couple of years ago," he says. "There was a laser show, just a huge thing, and we were the hosts. And these guys, with all their high-tech knowledge, just watched and said "Wow! How'd you do that?

"It's just a rotating mass, you know, just basic technology," he says. But it's transformed by the spirit of Yo.