The practice is also drawing the ire of several consumer electronics manufacturers, including Sony Electronics, which says it cannot guarantee the audio quality of these CD's on its players, and Apple Computer and Sonicblue, whose sales of popular portable music players might suffer if copy-protected CD's became the norm.
But the record companies, who largely blame piracy via computers and the Internet for the 10 percent decline in United States music sales last year, are defending the practice and planning to put more protected CD's into the American market.
"If technology can be used to pirate copyrighted content, shouldn't technology likewise be used to protect copyrighted content?" wrote Hilary B. Rosen, president of the Recording Industry Association of America, in a response yesterday to a query from a member of Congress. "Surely, no one can expect copyright owners to ignore what is happening in the marketplace and fail to protect their creative works because some people engage in copying just for their personal use."
The individual labels are being secretive about their market tests.
But Macrovision, one company supplying the industry with the new technology, said several CD's bearing its copy-protection system had been released by major labels in the United States and were being sold in record stores across the country.
"It doesn't have a big label on it saying `copy protected,' " said Brian McPhail, vice president and general manager of Macrovision's consumer software division. "But some of these have been pretty high distributions."
The executives at the Universal Music Group, part of Vivendi Universal, have been the most outspoken proponents of copy-protected CD's. Universal said it planned to release its second copy-protected CD in the United States later this month: "Enter the Life of Suella," the debut album of Pretty Willie, a St. Louis hip-hop artist.
"Assuming the technology continues to work, we plan to do more," said Larry Kenswil, president of the eLabs division of Universal. "The bottom line is that there's a lot of copies of our music out there in the world right now where no one is getting paid, and it's going to take technology to stop that."
But the technology creates problems of its own. A side effect of several of the anticopying technologies is that they prevent CD's from being played at all on some computer CD-ROM drives and DVD players designed to play standard CD's.
"More Music from the Fast and the Furious," released by Universal in December, will sometimes not play correctly on Macintosh computers, and people who listen to the CD on a computer hear poorer sound than they would on a CD player. A small warning on the label says it is copy-protected. It says: "Playback problems may be experienced. If you experience playback problems, return this disc for a refund."
In Europe, where Sony Music despite the objections of Sony Electronics has released about 70 titles with antipiracy technology, the CD's are labeled "Will not play on PC/Mac." BMG, part of Bertelsmann, was forced to drop copy protection on two CD's it released in Europe when consumers complained that the music would not play on their CD players.
But even if the technology evolves to work with more machines, it will continue to thwart what many consumers have come to regard as a fundamental right: the ability to copy music they have legally purchased for their personal use.
Music fans whose parents once copied LP's to cassette tapes now take for granted the idea that they can copy the contents of their CD's onto their hard drives. They can then make custom mixes of their music or transfer songs to portable MP3 players for their personal use. They can also burn CD's to sell illegally or log on to Internet services that let millions of strangers share unauthorized copies of their music.
What bothers some consumers is that the technology does not discriminate between legal and illegal behavior.
"Being treated like a criminal makes me want to act like one," said Ron Arnold, 39, of Royal Oak, Mich., who has 1,137 songs on his portable iPod player all of them paid for, he said. Mr. Arnold is one of hundreds of frustrated music fans who have registered complaints at the www .fatchucks.com Web site, which keeps a list of CD's that consumers know or suspect are copy-protected.
Many consumers who have purchased copy-protected CD's may not even know that their discs have the technology. The Macrovision technology, for instance, works by inserting distortions into the music; the company says the changes cannot be detected on an ordinary CD player. But those distortions make clicking and popping sounds when the files are transferred to a computer.
Sonicblue, the maker of Rio MP3 players, said it could easily produce software to enable consumers to copy songs from the protected discs onto their players but did not want to risk prosecution under the Digital Millennium Copyright Act, which makes it illegal to break copy-protection systems.
The record companies say they are working with technology companies to create more sophisticated strategies that will allow each consumer to transfer one copy of the music on a CD to a computer, and perhaps to a portable player as well. The next generation of copy-protected CD's may also include music videos and liner notes to sugar-coat the new restrictions for consumers.
But for now, the advent of silvery discs that do not quite act like CD's have angered Sony Electronics and Philips Electronics (part of Royal Philips Electronics), which co-developed the compact disc format, first introduced in 1983.
"We do not approve the use of the CD logo on such products," said Rick Clancy, a spokesman for Sony Electronics of America. "It puts us in a position where we can't guarantee the playability or sound quality of discs that may be used with our devices."
The written statement from the recording industry was prompted by a complaint about copy protection by Representative Rick Boucher, Democrat of Virginia. He said he believed that the companies were "seeking to use their copyright not just to obtain fair compensation but in effect to exercise complete dominance and total control of the copyrighted work."
He added, "I have told the heads of the major labels I think this is a major mistake that will engender a major public backlash."
That may be why the labels are not divulging much about their activities. A spokesman for BMG would say only that the company had so far released "a handful" of copy-protected titles in Europe, but he did confirm that one of them was "World of Our Own" by Westlife, an Irish band. Athena Espiritu-Santo, 28, who bought the CD at a store in San Francisco as an import, had already figured that out.
When the CD would not play in the CD-ROM drives of her computers, either at work or at home, where she usually listens to music, friends told her that it was probably copy-protected. Still, she does not want to return it.
"That would mean I wouldn't have my Westlife CD," said Ms. Espiritu- Santo, a legal assistant, "and they're kind of hard to find here." So she just listens to the CD in her car.