Fans of major recording artists are unwittingly buying compact discs that cannot be copied by computer. That capability, designed to prevent piracy, also prevents consumers from putting the music on their own portable listening devices. The CDs give no notice or other visible indication that they have this limitation.

The technology at work is SafeAudio, a product developed by Macrovision Corp. A company spokeswoman confirmed that CDs with SafeAudio embedded are on general sale in several nations, but all such deals with record labels are covered by nondisclosure agreements. She added that even she does not know which artists' products utilize SafeAudio, but she believes at least one major artist's protected work is on sale in California.

The CDs can still be played on a computer's CD drive or any other compact disc player.

SafeAudio works by exploiting the technology behind error correction codes. All compact disc players have error correction, but the mechanism works differently in computer CD drives than in compact disc players -- hence the inability to duplicate from a computer's CD drive.

Macrovision claims that its technology is inaudible and undetectable to listeners. The spokeswoman said that to the best of her knowledge, there have been no reports of complaints and no increase in return rates on the relevant titles.

SafeAudio does not require changes to the disc manufacturing process and can be engineered to permit authentication options for computer or Internet applications. Each title carries a unique protection code, which further inhibits potential piracy.