The most popular rock ensemble in the Soviet Union has come under a vitriolic public attack in which it was denounced as an "un-Russian" group that is raucous and is unable to sing in harmony and that uses lyrics loaded with "dangerous ideas."

The extraordinary assault in the newspaper Komsomolskaya Pravda, the official daily of the Young Communist League, came only a few weeks after the same paper announced that millions of its readers have selected the group Time Machine as the most popular ensemble of 1981.

Time Machine could in many ways be compared to the Beatles in terms of its originality, talent and influence on young Soviets. It earlier had been acknowledged as a trend-setter whose concerts and records are instantly sold out, and it symbolizes generational changes here.

The recent attack accused the group of spreading subversive ideas, cynicism, pessimism and generally hindering the furthering of communist ideals among young people.

The attack seems to reflect internal political disputes between younger and more modern elements in the party and the more orthodox older generation. The unusual about-face also comes against a backdrop of persistent reports of a power struggle in the Kremlin stemming from Soviet leader Leonid Brezhnev's fragile health and the recent death of Mikhail Suslov.

The attack on the group suggests that there are groups in the Soviet elite that would like to see a crackdown on pop music, which is now playing the role once filled by books, movies and television.

Recently published articles have suggested that pop music, blue jeans and sweatshirts are being used by the West to undermine socialism here. Yet Time Machine has been featured on the state-controlled television and its enormously popular concerts throughout the country are sponsored by the Young Communist League, known as Komsomol.

Only a month ago, a Soviet music critic wrote in the weekly Novoe Vremya that the group's lyrics dealt "honestly" with morals and other problems troubling Soviet youth. There is indeed a sense of apathy and aimlessness among young people here that official propaganda tends to mask with slogans.

Novoe Vremya acknowledged this by saying: "Their poetry is a statement, and their metaphors seem like slogans. There is something reminiscent of Bertolt Brecht's songs and political posters of the twenties in them. They deal with a whole range of moral, civic, personal and social questions that agitate Soviet youth."

The more recent attack, however, appears to seek to destroy the reputation of the ensemble by not only denigrating its musical abilities but also by showing it as "un-Russian" in an effort to exploit patriotic and ethnocentric sentiments of the older generations.

"An alien tree transplanted in our soil does not bear fruit," the article said in charging that Time Machine was not rooted in Russian national culture.

"Just as there is Central European time, so there is a Central European mold. We would like to see Soviet groups fit into a Soviet mold, just as they stick to Soviet time."

The lyrics of the group, written by its leader Andrei Makarevich, appear to challenge official Soviet propaganda. Yet the group's very popularity indicates the wide resonance it has gained among millions of Soviet youths.

"I do not believe in promises," the group sings in one of its songs, "and will not do so in the future. There is no point in believing in promises any longer."

Another tune says, "We have given our word not to turn off the straight path. But, fate forced us to." Yet another tune, which runs counter to the official belief in progress, says: "Tell me, why are you happy? Wait, look back, and see how the fallen leaves decay, how a crow circles where once a garden bloomed."

In criticizing the last tune, the paper stressed that the five-member group gave political significance to it by singing the word "crow" in a major key.

Other songs to which Russian audiences respond with enthusiasm include the notion that the "bluebird of hope," the symbol of future happiness in traditional Russian folk tales, has vanished from young people's lives.

"You have to wear masks, wear masks, because only under the mask can you remain yourself," another song says. Yet another says, "I am calm only for the fact, that now nobody can deceive you, and you are now prepared to do things for yourself."

Other songs by the group talk about loneliness and about "one sunny day when millions of young men died with song on their lips."

In taking on the popular group, Komosomolskaya Pravda sought to portray it as a poor imitation of Western pop groups. Time Machine, it said, sought to overcome its artistic inadequacies by appearing in "gaudy rags"--tights, sneakers, beach hats and ropes around their necks.

The paper spoke of the men's "infantile" use of falsetto.

"This way of singing, while wearing beards and moustaches, obliterates any masculine qualities in performances and in their artistic stand. To hear a normal male voice used in ensembles in this way has become a problem. Men, sing like men!"

Despite the vitriolic attack, it does not seem likely that the authorities would move against the group at this stage. -