How could music contain hidden information?

Audio watermarking started in the 1990s as a modern and very technical version of playing cat and mouse.

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The music industry, dominated by the “big four” record groups, also known as the “Majors” (Sony BMG, EMI, Universal, and Warner), quickly realized that the availability of digital media for music recordings and the possibility to transfer it fast and degradation-free (thanks to the availability of high data-rate networks and of efficient data compression standards) would not only offer many benefits in terms of market expansion, but also expose their business to a great danger: that of piracy of intellectual property rights. Being able to insert proprietary marks in the media without affecting audio quality (i.e., in a “transparent way”) was then recognized as a first step toward solving this issue. Additionally, ensuring the robustness of the proprietary mark to not only to usual media modifications (such as cropping, filtering, gain modification, or compression) but also to more severe piracy attacks quickly became a hot research topic worldwide.