Make your meals `sing' with cheese, beef and -- Mr. Potatohead?

Milk. In a dozen ways, the message is projected in the conference room of this Chicago hotel:

``Have more milk 'cause milk's got more,'' goes one TV jingle.

``Make your meals sing with cheddar cheese,'' says a full-color magazine ad, one of three being passed out.

The audience of men and women listen attentively. Then, without dissent, they approve the ads -- part of a $64 million promotion campaign.

Welcome to the latest meeting of the National Dairy Board -- an appointed group of 36 dairy farmers plus staff, whose sole job it is to boost sales of dairy and dairy products.

``If we could get everyone to drink one more glass of milk a week, we could destroy the [dairy] surplus,'' says Joe Westwater, the board's plucky chief executive officer.

In some ways, the board is a sign of the times in United States agriculture. Stuck with burdensome surpluses or the prospect of flat sales, producers of a number of different commodities are reaching the same conclusion: To boost sales, they'll have to advertise.

``We all realize that we've got to start acting like the food industry rather than producers,'' says Jeanne Sowa, promotion manager for the Beef Industry Council. ``The challenge for us is to show that beef can be fun -- that it doesn't have to be roast beef with mashed potatoes or meatloaf.''

The trend toward more generic advertising -- called generic because it advertises a food rather than a brand name -- is not particularly new. But just now there is a flurry of activity.

Cattlemen, for example, are preparing to vote on whether to set up a national beef board. The American Beekeeping Federation wants Congress to authorize a honey board. If both succeed, that would bring to eight the number of commodity boards specifically authorized by Congress, including the American Egg Board, the Cotton Board, the Potato Board, the Wheat Industry Council.

Meanwhile, 21 of 48 fruit-and-vegetable grower groups also have set up research and promotion programs. They range from California almonds to Florida limes, Idaho-Oregon onions to Hawaiian papayas.

Why all the interest? There are many reasons.

Consider the plight of Doug McGinnis. A partner in a honey producing and packing company in Edgewater, Fla., he has seen a sharp drop in retail and export sales. The company has begun packing surplus honey for the federal government to stay in business.

``But that won't last forever,'' Mr. McGinnis says. ``We're quite convinced that people need to eat more honey.''

In almost all cases, though, the promotion efforts come at a price. Usually, farmers fund the programs themselves by paying a kind of mandatory or voluntary tax on whatever they sell. To fund the large dairy promotion programs, for example, dairymen are required to chip in 15 cents for every 100 pounds of milk they sell. Apparently, the idea isn't controversial: Last month, 89.7 percent of dairymen voting approved a continuation of the 15-cent assessment.

For the board members meeting here in Chicago, news of the vote is one of several encouraging signs. After decades of decline in milk consumption, the industry saw a dramatic 3.5 percent increase last year. Even more encouraging, 1985 could register another 1 percent boost in commercial sales. Meanwhile, a six-week summer promotion of ice cream, which was coordinated with brand-name advertisers, scored well.

The problems, according to the board's advertising evaluation committee, lie in the cheese and butter campaigns. Cheese and butter are key, Mr. Westwater says later, because it takes 10 pounds of milk to make 1 pound of cheese; 20 pounds of milk for 1 pound of butter. But the advertising, geared to home use, had no discernible effect on at-home sales. The board votes to let the committee come up with new options.

With an advertising budget of some $65 million, the dairy campaign dwarfs other generic advertising. In its first year of operation, the board became the nation's 33rd-largest TV network advertiser.

But compared to the mammoth advertising campaigns for brand-name food and beverages, generic advertising is a drop in the bucket. In 1982, for example, generic advertising made up only 2.1 percent of the $3.6 billion spent on all food and beverage advertising, according to an agriculture department report.

Given such small resources, can generic advertising work?

``Yeah, we'd have to say it's very successful,'' says William Gordon, marketing director for the Florida Department of Citrus. ``We've had 50 years of unbroken advertising support and straight-line increases year by year.''

In the 1950s, the Florida growers began promoting a new product -- frozen orange concentrate. First, Mr. Gordon says, the ads aimed at moving the juice from an occasional to an everyday breakfast drink. (Remember Anita Bryant and ``A day without orange juice is like a day without sunshine?'') The next target was to broaden its appeal: ``It isn't just for breakfast anymore.'' And the current ads -- ``Orange you smart'' -- target the juice's nutrition. Throughout, Gordon says, the ads have stressed big se rvings by showing orange juice in large glasses.

Now, however, the growers have another problem. A series of devastating freezes in Florida have severely reduced the crop, meaning that nearly half of US demand now has to be met with imported oranges, particularly from Brazil. So, beginning this week, the growers are kicking off another nationwide campaign, giving juice packers a Florida seal of approval when they agree to pack to that state's standards.

``The long-term goal is to assure the consumer of constant quality and to retain a strong Florida presence until we are strong again,'' Gordon says.

Until this year, there was no solid evidence that generic advertising affected sales. But according to preliminary figures from a study of the National Dairy Board's campaign, a 0.3 percent uptick in milk consumption was directly due to milk advertising in market sample studies.

Traditionally, generic campaigns have measured success by how much they've changed consumer attitudes.

When officials at the Denver-based Potato Board realized that consumers had an unwarranted negative opinion about the potato, they got to work. In a recent magazine ad, for example, they disguised a potato with nose and glasses `a la Groucho Marx. Above the full-color ad ran the caption: ``Can you recognize America's favorite diet food?''

Now, the board is feeling confident enough to move into other areas, says A. J. Otjen, consumer relations director for the board. It's looking into campaigns for potato chips and French fries. The message: ``It's just another slice of potato.''

That message seems a lot less controversial than the recent ``Beef gives strength'' campaign by the Beef Industry Council. A nonprofit consumer-health group in Washington labeled the beef ads the most misleading of the year.

Overall, generic advertising seems to be gradually increasing.

``I think it's the continuation of a trend,'' says Dr. William Manley, an agriculture department official responsible for overseeing the promotion programs. From 1972 to 1982, spending by farm commodity associations tripled, according to Leading National Advertisers, an advertising research firm.

Advertising alone isn't going to solve agriculture's long-term problems, says Clifford Carman, an Agriculture Department dairy analyst.

Just ask producers of wool. Theirs is the oldest promotion program specifically authorized by Congress, but they have seen the product lose out to man-made fibers. In 1950, four years before the promotion program was enacted, wool claimed 10 percent of US fiber use; by 1983, it was down to 2 percent.