It's the unreal thing. It's the pause that depresses. It is not It. It is something else again.

Coca-Cola, which once said it would like to teach the world to sing in perfect har-mo-nee, is now hearing a chorus of discord about the fact that for reasons unfathomable to the normal human with a thirst to quench, Coke has changed its formula from the one America loved to a new one America isn't quite sure about.

Gay Mullins, 57, a retired Seattle businessman, is sure about it. He hates it. He hates it so much he has sunk $30,000 of his own money into a war chest ("We're going through it so fast," he says) and founded Old Cola Drinkers of America, a group he says will pester, petition and even sue Coca-Cola if necessary to get the old Coke back.

"It's no joke," Mullins says from Seattle, where his 900-number hot line plays a rabble-rousing recorded message ("Let's Get Coca-Cola to start making that old Coke again -- or release the formula so someone else can!") and counts each call as a vote against the new Coke. "I'm mad. This makes me angry. I'm angry, and I'm mad. I feel injured. Betrayed. Like a sacred trust has been violated, something torn out of the American fabric. I know people who are going through withdrawal without their Coca-Cola. People are having anxiety headaches. They've been placed in a distressed state. It's the post-Coke syndrome. People are so shocked by this, they worry that maybe the whole country is beginning to fall apart. They don't even trust themselves anymore."

Coca-Cola was like "coffee, tea, baseball, the westerns" -- a part of the American experience -- Mullins says, and for the company suddenly to ditch the taste that had everybody hooked for six decades is irresponsible. "Why, it's even un-American," he says. And so he is not only collecting petitions and totaling up the phone calls, he is talking lawsuit. First he thought of a class-action suit but found there were no legal grounds. Now he's considering suing to force Coca-Cola to release the secret recipe for the old formula.

He would prefer, he says, for the company simply to say, "Ooop. We're glad you told us, America. We did wrong and starting tomorrow we'll bring the old Coke back." Not bloody likely. Ken Coleman, a spokesman for Coca-Cola in Atlanta, says that while "We really don't have any comment on that group" in Seattle, "Indications on the reformulation of Coke are very positive. The new taste is doing quite well." Coleman says that more than 190,000 consumers participated in months of blind taste-testing before the new taste was introduced. "So we're confident that the new taste will succeed."

Coke has denied the charge made in an anonymous letter sent to Advertising Age, the industry trade publication, that 95 percent of the 2,500 calls a day to Coke's 800-number consumer hotline, plus 40,000 letters a week to the company's headquarters, denounce the new Coke formula as intolerably icky.

There have been 40,000 calls and letters, Coleman said yesterday, but they aren't all negative. "Some ask why the change, others ask where to get the product, and there are some negative comments," he said. "A few ask about the best way to store the old Coke if they want to stockpile it." The Associated Press reports that a Beverly Hills liquor store is selling the old Coke for $1.25 a bottle, $30 a case.

But Mullins says overwhelming response to his campaign proves the new Coke is a fizzle, not a fizz. Those who spend the 50 cents to dial the 900 number (900-410-2000) hear, in addition to that soul-stirring message, updated daily, a country-western jingle ("I want to teach the world to sing, 'Please don't change the taste of Coke' ") contributed gratis by a concerned composer from Tennesee. A Texas minister has offered to be chaplain for the movement. Petitions are circulating in San Francisco, New York, and other cities. "It's just snowballed," Mullins says merrily.

"The CBS Evening News" is working on a story about Mullins and his movement; he is giving interviews left and right and making talk show appearances on radio stations in the United States and Canada; and on Monday, Mullins is scheduled to appear on ABC's "Good Morning America" to debate representatives of the Coca-Cola company on this taste business, one of the great issues of our time. Or our week, at least.

Operators are standing by in Seattle to take calls at a 206 number to which those who call the 900 number are referred for more information. Hundreds have done so and talked "for minutes and minutes" on their own money, Mullins says, because they are so upset. So far, though, there hasn't been much financial assistance offered Mullins to help defray his $15,000-a-week telephone bill. "A total of one dollar has come in," Mullins says glumly.

Mullins did indeed try the new Coke. "It tasted flat and it left a soapy taste in my mouth," he says. "It didn't have zing to it. It was like they took a day-old Coke and put a couple of spoons of sugar in it." He concurred with one popular impression of how the new Coke tastes: "Like a flat Pepsi."

Up in Purchase, N.Y., at PepsiCo headquarters, they've heard that charge, and how it tickles them. "I think they're probably right," says Rebecca Madeira, director of public relations. "Coke has upped the sugar level so that Coke is sweeter than Pepsi. It always used to be that Pepsi was sweeter than Coke. Who knows what they've done with the oils and the other stuff in it."

Pepsi is capitalizing on the trauma wrought by Coke's change in taste with aggressive TV and radio ads in which consumers wonder Why Coke Changed. Hmmmmm. Asked if the change might be considered a godsend to Pepsi, which has always lagged behind Coke in total sales, Madeira said, "It is, sure. Here we are heading into the key selling month of July, when even non-cola drinkers want a cola, and they do something like this. Oh, how embarrassing!"

Coke and Pepsi sales are measured in Nielsen rating points, just like TV shows. The new Nielsens aren't in yet because figures have yet to catch up with introduction of the new Coke taste. But Madeira says Pepsi market research is conclusive: Only 18 percent of loyal Coke users like the new taste, 65 percent of new Coke "tryers" rate it as too sweet ("and it is," says Madeira -- "13 calories sweeter"), 57 percent of new Coke tryers rate it weaker than old Coke and 46 percent say they may switch to another brand.

Oooh, they don't like that kind of talk in Atlanta. Coleman at Coke has his own figures: of 110 million people who have tried the new Coke taste, 75 percent say they will buy it again. Unit shipments to Coca-Cola bottlers in May were up 8 percent over May 1984. And so on.

All this means nothing to the both angry and mad Mr. Mullins.

"The old Coke had a distinctive taste," he says nostalgically. "I remember drinking it during World War II, when I was in the Caribbean. I had Cuba Libres rum and Coke , and to me, that was the height of sophistication. And here I am now unable to have what I had in my youth. I'm not a drug addict. I just like Coca-Cola.

"To those of us who love Coca-Cola, there was something special about it. We live in a capitalist system that allows us choices. Now our choice has been taken away. We have the feeling like we've got creeping communism or something. I hate to say that a company that has made as much money from capitalism as Coke would have anything to do with communism. But I just think they made a corporate booboo, and they're going to have to rectify it."