Let's say you are an NFL linebacker who loves Willie Nelson music. Let's say you want to be a better player. So you hire Hal Becker,Ph.D., to put together a subliminal pep talk. You pop the cassette into the tape player of your Jeep.You hear the words printed here in italics. The capitalized words are the subliminal messages, unheard but perceived by your subconscious. They are repeated time after time until Willie finishes his wailing.

"Mamas, don't let you babies grow up to be cowboys . . ."

AGGRESSION IS OKAY.

". . .Don't let 'em pick guitars and drive them old trucks. . ."

CONCENTRATION IS IMPORTANT.

". . .Make 'em be doctors and lawyers and such ."

I NEVER QUIT.

For 30 years, Hal Becker's work in subliminal perception was ignored as too, too 1984ish. The specter of thought control -- Big Brother not only watching us but stealing into our minds -- is so frightening that the Federal Communications Commission has banned subliminal messages from television. No such regulations exist in Hollywood, where "The Exorcist" included subliminal pictures of a terrifying death mask, but pressure from public interest groups ensures such stunts won't happen often.

Eric Lander, in the February issue of Omni magazine, reports that subliminal perception now is used to test Swedish Air Force cadets. Looking at a picture that appears for 0.004 second, a cadet must instantly interpret its meaning. "If his subconscious fails," Lander writes, "he will be found unfit to fly." Subliminal messages in Southampton, England, help agoraphobics overcome thier fear of open spaces. Israeli math students perk up after ultrafast messages tell them how good they are. New York City women lose weight with subliminal suggestion.

By definition, subliminal messages are delivered by pictures or sounds so fast or so faint they are perceived only subconsciously. Subliminal researchers such as Dr. Becker insist such messages cannot be used to turn people into zombies doing the devil's work. Becker says a subliminal message only reinforces a person's attitudes, it doesn't change them. Not all scientists agree, and research goes on.

Meanwhile, we have Dr. Becker's Balck Box.

President of the Behavioral Engineering Corporation in Metairie, La., Becker, 58, holds degrees in electronics and physics from Tulane University, where he was a professor for 27 years. On Oct. 11, 1966, he was granted a patent for what is known informally as Dr. Becker's Black Box. The box, mixes subliminal messages with music, most effectively with Muzak.

Hidden in the rear of a big New Orleans Supermarket, the Black Box whispers a subliminal message over and over: "I am honest . . . I WILL NOT STEAL." The store claims it works, that no longer do customers and employes steal $100,000 worth of food every year.

Becker's honesty enhancement program, as he calls it, has evolved into a variety of applications with 35 Black Boxes installed in 15 businesses such as department stores and real estate offices (where the whisper is: "My TIME IS VALUABLE . . . DOLLARS NOW . . . REWARD IS COMING.")

For 30 years, Becker has believed in the goodness and power of subliminal messages.

He won't use them indiscriminately. "it's not that I think they could make everybody into a bunch of zombies to get them to go against their will. They couldn't be used that way. It likely would produce just the opposite effect. But I just don't think advertising, politics and religion are appropriate fields."

Becker believes subliminals have a legitimate public use.

"The commissioners of the FCC could become heroes overnight if they approved TV subliminals on automobile safety," Becker said. "It tears me up to see the terrible toll of auto accidents when I know subliminals would help it."

And, yes, someday our NFL linebacker will be massaged subliminally on his way to the ballpark.

"A professional football player read the Omni article and called, too," Becker said the other day. "He wants to look into the possibility of a custom-made subliminal program for him."

In the 20 months since the Black Box went on the market, several pro football teams have requested such information, Becker said. Even before that, he did some sports work but Becker wouldn't say with whom because he has an agreement of confidentiality with his clients.

"I feel sure subliminals helped in our sports work," Becker said. "But I'd rather not talk about that until we have enough data without question or doubt to demonstrate success."

What if, say, the woebegone New Orleans Saints asked for a Black Box? Would Becker work with the NFL's worst team?

"Hell, yes," he said.

Here's how Becker would do it. First, he would get his $5,000 to $10,000 fee in advance.

"That's to get management's attention, to show them this isn't frivolous, and to make sure they're not doing it on a stunt basis to try to pull one game out," he said.

Then Becker would sit down with each player, coach and front-office type for a kind of psychological probing to "analyze what he feels are those behavioral attributes that would make him the best in the world at what he does."

For our Jeep-driving linebacker, those attributes might be, in Becker's words,"Aggression is okay . . . concentration is important . . . I NEVER QUIT.

"Then we take his favorite music and embed these affirmations in the tapes," he said.

And would the Saints be better for this?

"Hell, yes," Becker said.