For your ears only [copy controls for CDs]

After recordable CDs hit the market in 1991, momentum on copying the discs began to build. Copies of original CDs were perfect and could themselves be copied ad infinitum. When blank disc prices dropped, people began copying CDs for their friends, just as they had with cassettes. As a result, recording companies began looking for ways to put the genie of infinitely copyable digital music files back into the bottle, based on the Red Book standard. Some of the techniques being used by the industry are discussed in this article.