Rio Brio: A Rock Extravaganza : Pop music: Promoter and ad executive Roberto Medina compares his Rock in Rio II to Woodstock. Others see it as a clone of the L.A. Olympics.

Six years after staging one of the world’s largest rock festivals here, Brazilian advertising impresario Roberto Medina is back with an ambitious encore that could become the prototype for megaconcerts in other parts of the world.

With characteristic hyperbole, Medina--the 43-year-old president of the Rio advertising agency Artplan Empreendimentos e Participaoes S.A.--is comparing his 10-day, $20-million Rock in Rio II extravaganza to Woodstock.

And observers are making much of the fact that the event, which began on Friday, follows the October debut of MTV in Brazil and the release of Paul Simon’s Brazilian-influenced album “The Rhythm of the Saints.”

But with financial backing from Brazil’s TV Globo television network and Coca-Cola, the festival--which features more than two dozen of the world’s biggest pop-rock acts, from Prince to George Michael--is shaping up more as a free-enterprise clone of the 1984 Los Angeles Olympics than the landmark Woodstock event.

“It’s not like Woodstock,” said Doug Herzog, senior vice president for programming at MTV, which will air the festival next month. “This is a huge commercial event. . . . It offers bands global exposure.”

Despite the high expectations, it seems incongruous that this huge and costly festival is unfolding in a nation burdened by crushing poverty, widespread illiteracy and the largest foreign debt in Latin America.

But Medina, a flamboyant, image-conscious businessman, has earmarked revenue from one night of the festival for a Brazilian homeless children’s charity, along with some proceeds from a live album produced from the concert.

“Rio de Janeiro will regain its position as the world’s youth capital with Rock in Rio,” said Medina, who seemed flattered when compared to Donald Trump. “I don’t know what Trump’s motivation is--I don’t know if he likes (New York City) as much as I love Rio. But we are going to create magic here.”

Medina, who says he first got into the concert business in 1978 after making a Brazilian TV commercial with Frank Sinatra, has been engaged in his own battle of sorts against critics bent on derailing his festival.

His most crucial fight came only a few days ago when a local man complained to authorities that Maracana Stadium, which had been closed to some soccer games last year because of safety concerns, might be too unsound to hold 117,000 rock fans.

But Medina’s representatives convinced a judge that the complaint was unwarranted and that the show must go on. Medina says he made some structural improvements to the stadium nonetheless.

The official estimates of paid attendance for the Friday and Saturday concerts were 70,000 and 80,000, respectively, though the stadium was nearly full because of guests and media members.

Reggae singer Jimmy Cliff’s performance was a clear favorite at the opening show. Headliner Prince has a hard time keeping the crowd’s attention because he took the stage at about 2 a.m. and didn’t conclude until 3:30.

Guns N’ Roses was the big attraction at Monday’s hard-rock oriented show, which also featured Faith No More. But the controversial Los Angeles band’s surly attitude at a press conference and its obscenity-laced performance alienated the Brazilian press.

Renato Costa, who handles promotion of international artists for Polygram do Brasil Ltda., said that Brazil is the world’s fifth-largest music market and can be very important for artists.

For example, he said, “Who is Jimmy Cliff? He hasn’t (had a hit) in years. But he’s so popular in Brazil. The people loved his concert.”

By contrast, Costa said, “Guns N’ Roses disappointed a lot of people,” because they weren’t as solicitous of Brazilians.

Record companies, who saw their Brazilian sales climb between 20% and 35% in the year after the first Rock in Rio in 1985, are hoping this year’s festival will spark a similar increase in album purchases.

“Rock music has grown tremendously in popularity since Rock in Rio I,” said Manuel Camero, president of the Rio-based label, BMG Aeriola Discos Ltda. “I expect to see several groups selling more than 1 million records in the next two years” if Rock in Rio II is a success.

Financial success, at least, seems virtually assured given Medina’s massive international publicity build-up.

The festival has been the talk among many in the music industry, said John Marx, head of the William Morris Agency’s music division in Los Angeles. And Marx said he thinks similar megaconcerts may be tried outside of traditional venues because there is a growing appetite for rock music in emerging markets such as Latin America and Eastern Europe.

But Medina is not just pinning his hopes on local fan attendance. He estimates that just 35% of the total revenue for Rock in Rio will come from ticket sales.

Medina expects to earn most of his money from a variety of merchandising and licensing deals that have made this one of the most commercialized live events in music history.

Instead of only selling traditional concert fare like T-shirts and food, Medina has rented out the huge Maracana Stadium to about 60 vendors who are hawking everything from clothes and jewelry to books and videos.

He has struck 20 licensing deals with companies to make products for the concerts, including a specially designed Coca-Cola container that will be sold to music fans.

More revenue will come from various television rights and a record deal.

Medina won’t say how much he expects to make. But he predicts that the festival will lure more than 1 million fans. The Brazilian press reported Tuesday that ticket sales and concessions had so far yielded 1 billion cruzados (about $5.2 million U.S.).

Unlike the first Rock in Rio festival, which featured jazz guitarist George Benson and Brazilian fusion artist Ivan Lins, this year’s lineup is dominated by rock’s hard core: Billy Idol, INXS, Guns N’ Roses, Queensryche, Megadeth and Run-D.M.C.--among the international groups--and Labao and Engenheiros do Hawaii among the local talent.

But rock’s hard edge was tempered somewhat by the inclusion of a smorgasbord of other artists that appeal to a variety of tastes.

Those ranged from rock veteran Cocker and teen idols New Kids on the Block to the retro-disco act Deee-Lite and Cliff.

But despite the eclectic lineup, there was no pleasing everyone.

Some U.S. music industry executives have complained that there are no women rockers and only one rap act. One Brazilian traditionalist complained that the rock festival featured no indigenous music.

“Rock in Rio is more for the international musicians than the Brazilians,” said another observer, Rio musician Marcelo Ferreiro, who backed up Brazilian rock star Labao. “We play only for (the pleasure of) the music.”

Perhaps to underscore that sentiment, both Labao and Medina--in last minute gestures--decided to include Brazil’s beloved samba music in the Rock in Rio festival.

“This is a rock concert, of course,” said Medina, “but it is also a good opportunity to show our music to the world.”