The RedBook standard -- named after the red binder it first appeared in -- was defined by Phillips and Sony in 1982, back when Shawn Fanning was still crawling around bear rugs. Quickly Sony and Phillips realized that the CD could also be used to house computer files, and in 1984 the two companies developed the somewhat different YellowBook standard for data storage. (Phillips and Sony finalized the OrangeBook standard, for rewritable CDs, in 1995.)

Unlike vinyl records, which store music in a continuous spiral, RedBook CDs -- the CDs owned by every music fan -- break up music tracks and distribute them higgledy-piggledy around the disk in "sectors" that are similar to the data sectors on computer hard drives. Because the data are scattered all over the disc, each CD has a "table of contents" that tells the player where to find each track. RedBook CDs run a maximum of 74 minutes and can hold at most 99 tracks -- if a CD is longer or has more tracks, the player won't know how to read the extra music. Importantly, the music sectors on a CD are interwoven with additional error-fixing data that the player's built-in software uses to reconstruct the tracks if dirt or tiny air bubbles from the manufacturing process make little chunks of the disk unreadable.

CD-ROMs, which are also used for computer software, are different. Because CD-ROMs may have hundreds or even thousands of files, they need to handle many more than 99 "tracks," which means they have different, larger tables of contents and can, in theory, hold up to 100 minutes. Because computer programs can't just skip a bit of code if the disc is dirty, CD-ROMs are more exacting about error correction. For that reason, a YellowBook CD-ROM devotes an extra chunk of each data sector to a second method of detecting and fixing flaws.

According to label executives and audio engineers, copy-protection firms take advantage of these differences by adding extra data to both the tables of contents and the music tracks -- data that are ignored by CD players but confuse CD-ROMs. One purchaser of the Midbar-protected version of Razorblade Romance, for instance, reported on Slashdot that an Onkyo CD player had no trouble with the CD, but Cdparanoia, a powerful open-source ripping program, could extract only 30 seconds of it. The CD player, the Slashdotter wrote, displayed "a playing time of 100 minutes, 30 seconds -- not! ... So the trick seems to be that the playing time of 100:30 is interpreted as 00:30." The literal-minded computer software, he suggested, stopped when told it had reached the end, whereas the "hifi-player also says 00:30 of course, but after 30 secs it goes down to 99:59" and plays normally. Asked about this account, a Midbar representative said the firm "cannot provide more technical information at this time."

Although audio engineers say that planting false data in the table of contents is part of every copy-protection scheme, they also aver that the most important copy-protection techniques involve adding actual errors to the music. When a standard CD player comes across an error in a CD, says a technology officer at a major label, "it basically skips over it and keeps playing. But a CD-ROM must read every bit of the data. When it detects something that it suspects is an error, it loops back and rereads the data, trying to discover how to fix the problem. And ultimately, if the error can't be corrected" -- as is the case with the "erroneous" data introduced by copy-protection programs -- "the software will cease to run and the CD-ROM will stop playing."

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