Storing Data in Music

Intriguing idea, in theory not that hard.   Why might it be used?  A kind of Steganography?

Storing Data in Music 
ETH Zurich
By Fabio Bergamin

Researchers at ETH Zurich in Switzerland have developed a method for embedding data in music in a way that is imperceptible to the human ear, and transmitting it to a smartphone. The researchers found that under ideal conditions, the technique can transfer up to 400 bits per second without the average listener noticing. The researchers used the dominant notes in a piece of music, overlaying each of them with two marginally deeper and two marginally higher notes that are quieter than the dominant note. The team also used the harmonics of the strongest note, inserting slightly deeper and higher notes there as well. The data is stored in these additional notes. Said ETH’s Simon Tanner, “What we’re doing is embedding the data in the music itself; transmitting data from the loudspeaker to the mic.”  .... '