Songwriter Sammy Cahn and four music publishing companies have filed a class-action suit against Sony Corp. to halt sales of its recently introduced digital audio tape recorders, reopening an emotional copyright fight that Sony and other manufacturers of the machines had hoped was finished.

The plaintiffs contend that by selling the new-generation machines, which can record music from compact discs with the same sound quality, Sony is "inaugurating a new era in unauthorized home taping of copyrighted musical compositions" that will rob them of royalties.

Filed yesterday at U.S. District Court in Manhattan, the suit asks that home copying of recorded music using the machines be declared illegal. Currently, law enforcement authorities do not consider the copying of recorded music for personal use to be illegal.

Sony, which this summer became the first company to mass-market the machines in the United States, yesterday called the suit "totally without merit" and said it would continue selling DAT machines. The suit "seeks to hold this newest digital technology hostage and threatens to deny its benefits to American consumers," a company statement said.

The suit is the latest round in a fight pitting new consumer technology against protection of intellectual property rights. It recalls one filed against Sony in 1976 by Hollywood film studios over what was then a new product, the videocassette recorder. The studios lost that battle, with the Supreme Court ruling in 1984 that taping of TV shows off the air at home for personal use is legal.

Gary Shapiro, vice chairman of the Home Recording Rights Coalition, which includes recorder manufacturers, predicted that the new suit would fail on the precedent of the 1984 decision. He denied that home copying harms music companies and artists, saying that it in fact stimulates sales as people buy an album, then tape it to use in the car or to remove portions they do not like. "Every study has shown that people who tape the most buy the most," he said.

But Gary Hoffman, an attorney specializing in intellectual property, said the 1984 decision may not apply: The new suit explores "an undecided area," he said. "It will be a major case."

The suit asks for a ban on the sale of digital recorders and blank digital tapes. However, the National Music Publishers Association, which is working with Cahn and the music publishers, has in the past proposed a compromise under which the machines could be sold if some system were put in place to collect money to make up for lost royalties.

Japanese electronics companies first put the digital audio recorders on sale in Japan in 1987, but mass-marketing in the United States was blocked by threats of legal action from the Recording Industry Association of America, which represents major record companies.

Last year, however, the association and manufacturers reached a deal by which machines sold in the United States would be built so that they could tape compact discs, but not the taped copies. This was meant to serve as a brake on copying, because the person would always have to have an original disc in hand.

However, groups representing publishers, whose business is the promotion of artists, and songwriters havecomplained that the deal did not protect their interests, resulting in yesterday's suit.

Cahn has written or co-written such popular standards as "High Hopes," "All the Way," "I Should Care" and "Three Coins in the Fountain."