WARSAW, SEPT. 13 -- It was billed as the biggest, freest, most daring rock concert ever staged in Poland. And sure enough, when the home-grown group Perfekt hit the stage of a huge outdoor stadium here last night, 40,000 waiting young people jumped up to dance, shout, and sing out their frustration with communist rule.

"I'm not dead yet," shouted Perfekt leader Zbigniew Holdys, to the opening bars of a three-hour hard-rock show driven by the twin themes of alienation and defiance. At its end, his band was nearly drowned out by the crowd as thousands held up flames and sang out the words of the group's anthem, "We want to be ourselves."

What happened in between was a distinctively Polish show, where a base of blasting guitars was topped by gestures of protest ranging from the ironic to the explicit. At one point, thousands in the crowd added a word to a Perfekt chorus and repeatedly sang, "Don't be afraid of that Jaruzelski," Poland's ruling general and Communist Party chief.

During another song, the bearded, beret-capped Holdys segued into a guitar rendition of "Yankee Doodle" as the stage lights turned red, white and blue, bringing a huge roar of approval from his fans.

"You may have heard that the 'Days of Polish Culture' are going on in Moscow now," Holdys told the crowd, referring to an official communist-sponsored cultural event. "All the {party} guys went there, so we are free to jump around up here."

In fact, the concert marked a breakthrough for the Polish rock scene, six years after it came to life -- during the era of the Solidarity union movement. Politically explicit lyrics were banned after the union's suppression under martial law.

Subsequently, the groups were condemned by state music agencies to a wasting regimen of low wages and punishing schedules. This produced a crisis of declining quality and public interest in recent years.

Now, as a new wave of liberalization in Poland eases censorship and controls on private initiative, rock groups are hoping to make a comeback with a younger generation yearning to articulate its frustration and hopes. "Young people now know that something is wrong with the system in Poland, although they are not sure what," said Holdys. "To be credible with them, we have to say so straight out."

Perfekt is one of several rock groups that mixes protesting words and gestures with its music and is tolerated by authorities anxious to show that Poland has embraced the policy of glasnost, or openness in public life, promoted by Soviet leader Mikhail Gorbachev. Although the references to Jaruzelski and other explicit lyrics led to the groups' banning in earlier years, Holdys and other rock activists said communist authorities now seemed willing to tolerate rock as a relatively harmless, if irritating, outlet for youth.

With last night's concert, Holdys and the Perfekt group intended to kick off the new era. Banned from performing in much of Poland during the early 1980s, the five-member group -- which sold an astonishing 1 million records at its peak of popularity in 1982 -- reassembled several months ago and began preparing a new set of songs.

Perfekt formed its own private musical agency to escape from the tutelage of state agents and planned last night's concert to burst through the small-town, small-hall restraints enforced by the state on rock until now. "We wanted to play what we never were able to do before," said Holdys in an interview. "We wanted to give the biggest concert ever given in Poland, to do what is done by rock groups all over the world -- but was never allowed in Poland."

Remarkably, official waivers proved the least of the group's problems. Although Poland had never before seen a rock concert in a stadium, Warsaw officials readily agreed to book the city's huge Dziciencolecia stadium, which holds 100,000 for soccer games, and censors cleared all but one of the group's new songs.

Holdys, who has spent most of his 17-year career struggling to get permission for performances, said authorities may have felt obliged to be compliant. "It was easier to give us permission than to have it get out that Perfekt was banned again," he said. "That would have upset a lot of youth and made it look like nothing has changed here."

The real trouble, Holdys said, proved to be obtaining sufficient electronic, sound and lighting gear in technology-starved Poland, and setting it up properly. "We had to borrow practically every speaker in Poland, and 90 percent of them didn't work," he said. "There are only five cordless microphones in Poland -- we got three of them."

In the end, the group's hard work seemed to pay off. Despite sprinklings of rain before and during the concert, the sound system held up. Colored stage lights, swirling smoke and a climactic fireworks display made up a respectable spectacle. Most importantly, the hoped-for crowd of teens, students and young couples turned out, many of them riding in on trains and buses from outside Warsaw.

Holdys, although never a member of Solidarity, dressed for the occasion in a long black cape adorned on the back with a huge letter "S." "That's all it takes," he said with a grin. "Everybody knows what it stands for."

Although not overtly political, the songs were blunt in their messages. "A lot of us -- few of them," began one of Holdys' songs premiered at the concert. "They are afraid of us, they are afraid to sleep at night . . . they are afraid of themselves."

Another new song playfully focused on Warsaw's huge and popularly despised Palace of Culture, a gothic Stalinist skyscraper placed in the center of the city as a "gift" from Soviet ruler Joseph Stalin in the early 1950s. In a bitter comment on the failures of communist rule, the song speculates that the building, "that palace of ours," could soon collapse, "mixing the blood of the latest generations with that of the guy who falls from the 30th floor."