About 15 years ago I read an NYT article where all corporate audio, at least of the musical variety, had if codes embedded in the streams that passive listener devices could pick up.

I believe the point was for detection of royalty fees for public playback of songs.

I since have heard nothing about this, was that article true, and could you use it for this project?

The undercurrent of my interest was the pernicious tracking aspect, which is hilarious given it preceded the smartphone and it's active monitoring of everything you do