You may be interested in https://github.com/quiet/quiet-js https://github.com/quiet/quiet-js and https://danielrapp.github.io/spectroface/ https://danielrapp.gi

You may be interested in https://github.com/quiet/quiet-js https://github.com/quiet/quiet-js and https://danielrapp.github.io/spectroface/ https://danielrapp.github.io/spectroface/, both encode text / images over audible frequencies, but of course they sound weird. However it is technically trivial to encode "hidden" data at inaudible frequencies (>25 kHz) along with a song/whatever in the audible range and recover the data with a high pass filter. You would have to explain, however, the need for >48kHz sample rate. Another, stealthier option would be to encode information in the background noise of a recording, but this would require more complex encoding/filtering techniques.