WHEN country-pop singer Eddie Rabbit turns around in mid-commercial and tells his band it's "Miller Time," he's also heralding a new dimension in advertising: Madision Avenue meets rock music. The initial step taken by the rock band Journey four years ago -- redefining Budweiser as "the beer of rock and roll" -- has been cautiously followed by Charlie Daniels for Busch Beer, Kool and the Gang for Schlitz Malt Liquor, Mickey Gilley and the Commodores for Schlitz, Dave Mason and Rabbit for Miller.

Other examples: Michelob is sponsoring summer-long concert series at five major venues across the country, including the Merriweather Post Pavilion in Columbia; Budweiser, Stroh's and Schlitz also are bankrolling various series. At stake are the thirsts and minds of the millions of new beer drinking recruits to the $10 billion a year industry.

"Beer companies have always made efforts to go after the younger drinker, the new drinker, the one who doesn't necessarily have a preconceived image of a product," says Jay Coleman, head of Rockbill, a company that in the last five years has brought together a number of bands and breweries to provide posters and programs given away at concerts.

A number of factors have brought these unlikely allies -- the rock, brewing and advertising industries -- together at this time. Most important, the postwar baby boom is well over and there are simply fewer people entering the legal drinking market. Over the next decade, there will be a drastic demographic turnaround: The 18-21 segment will drop from 1980's 17,117,000, to 14,507,000, in the 1990s, while the 22-24 group will drop from 12,346,000 to 10,642,000.

As a result, breweries are having to fight harder than ever to maintain their phenomenal market growth. And since, according to Coleman, "the new drinker just developing brand loyalty is very susceptible to image, the breweries are trying to build a more contemporary image, to integrate the product into the life style of this audience."

Robert S. Weinberg heads a St. Louis research firm called Brewing Industry Research Program, or BIRP (he laughs about it; they don't), which serves a number of major brewers. He points out that the 18-21 and 22-24 age groups "are particularly important to the brewing industry. Their per capita consumption of beer is significantly higher than average. To offset these structural changes in the market, the breweries will have to apply one of two marketing strategies -- or both -- to try and capture for themselves a larger share of the market and to create a pleasant association with the product with as many people in those age groups as possible."

Though sports programming remains the prime vehicle for broadcast beer advertising, the younger audience seems less influenced by it. By federal regulation, sports endorsements may be made only by retired athletes, which is an ineffective avenue of "celebrity/status association" for younger consumers. There is no such restriction on musicians. "Entertainers can be currently performing," says Coleman, "and have a current appeal because they are in the public eye."

Coleman's Rockbills, a variation on Broadway's Playbills, are four-page, full-color program booklets containing bios and pictures of the featured celebrities. They unfold into 17-by-22-inch posters that can be hung on a wall. Coleman's research indicates that 95 percent of them are kept by fans. Rockbill tie-ins range from stereo equipment and wines and hard liquor to jeans, with the star personalities posing informally with the product. Typically, a foldout will show a band lounging around backstage holding cans of beer, label forward, "It won't say 'Charlie Daniels drinks Busch Beer,' but he'll be holding the can," Coleman admits. "We usually integrate the product in a noncommercial way . . . but we get the message across. The kids take them home, put them on their wall and [the sponsor] has a selling message that is more permanent than just one ad."

Can such sponsorship affect a band's popularity?Coleman feels that many artists are overly concerned with protecting their "image," even though they can get up to six figures to tie in to a beer. Journey is an example of the stunning potential of career development through tie-ins.

Journey's fans are a demographic dream for the beer industry: 30 percent are under 18 (approaching the legal limit), while 40 percent are between 18 and 21; 90 percent are white; 70 percent are male. Prior to Journey's Bud affiliation, only one of the group's first three albums had sold more than 200,000 copies. Its next album -- coinciding with Bud's first big radio promotion, sold 1.6 million copies and catapulted the band to super-group status. (In that ad, lead singer Steve Perry could be heard saying somewhat ungrammatically that "after a hot gig, we go backstage and we open ourselves an ice-cold Budweiser . . . 'cause there's nothing that quenches our thirst as good as Bud." The image-building really took off when Budweiser extended its support with print ads, T-shirts, lighters and a nationally syndicated radio broadcast. Beer manufacturers now sponsor a number of syndicated radio shows.

And image-building isn't necessarily limited to pop performers. Witness jazz vocalist Arthur Prysock, whose career received a needed boost five years ago when he became the voice of Lowenbrau. That commercial became so popular that Prysock, the first black artist to record a major beer spot, now includes it in his set. "It was very good for me," Prysock says, without revealing how much money he has received over the years.

Since 1973, Miller has run a series of ads featuring anonymous individuals in interesting professions breaking for "Miller Time." The Eddie Rabbit spots are the first to identify the individual. The use of Rabbit and other Miller spokesmen, like the Bellamy Brothers and Dave Mason, is seen as an attempt to get closer to the consumer since, Coleman points out, "the reason a young person drinks one particular beer has little to do with taste as much as it has to do with image."

The effect on Rabbit's career? Though it's hard to credit the ads entirely, his latest album, "Horizon," had peaked at platinum status and was already going down the charts when the Miller spots started airing in January. "Horizon" is almost double platinum now and, at a recent Chicago concert, the sold-out audience chanted "Miller Time" until Rabbit acquiesced with a few bars of the commercial before seguing into "I Love a Rainy Night." Rabbit also will benefit from greater recognition because his spots are mostly aired during sports programming, watched primarily by men, while his record-buying audience is primarily women.

Michelob's involvement in the summer-long series of concerts at the Post Pavilion underscores another direction in status association. "Most brewers have had some involvement with pop music, particularly through radio advertising," says Bob McDowell, group marketing manager for Michelob. "Summer's ideal because it's the high consumption period, and outdoors seems to work."

Michelob's sponsorship, through cooperative advertising and promotion, helps keep ticket costs down. There's no blatant selling or brand-pushing, but the residual benefits lie in community identification.At this time, Michelob has no plans to use celebrity acts the way Miller uses Rabbit and Mason, but if Miller's campaign seems effective, McDowell admits most of the other brewers will mimic them, "moving either defensively or jumping on the bandwagon, even if they don't know what the bandwagon is."

An interesting situation will develop on Aug. 22, when Kool and the Gang, spokesmen for Schlitz Malt Liquor, appear at the Michelob-sponsored Pavilion. Maybe Dave Mason could open the show?

As for parental and societal concerns that broadcasting beer commercials featuring pop idols will influence youth, Weinberg points out that "an enormous amount of research shows fairly clearly that beer advertising does not encourage somebody to drink beer; it only encourages someone to 'drink my brand rather your brand.'"

Jay Coleman expects rock celebrity endorsements to become more prevalent. He points out that the advertising trend in recent years has been to a narrower focus, or fragmented markets, something borne out by the broadcast ads currently in use: Kool and the Gang speak to a young black audience, Charlie Daniels speaks to 18- to 29-year-old whites, Rabbit exemplifies country music's broader based appeal of 18-49 with an accent on the down end.

Ten years ago, when rock was perceived as the vanguard of the political and social counterculture, Madison Avenue wouldn't touch it; conversely, many artists would have been (and may still be) hesitant about tying in with certain products if they felt their fans would reject such commercialization. But in the last five years, the industry has become extremely mainstream and the needs of Madison Avenue and the record industry are converging on an immutable point -- they are selling to the same people.