Aphex Twin embedded his own likeness in the waveformss of his song Windowlicker. As I understand it, the process works like this: Use metasynth to create sound waves from an image – in this case Aphex’ own face. When the music is played back and viewed with a spectrographic visualizer, the process is essentially reversed, which reveals the image in the sound waves. Kind of like steganography, but not. Does not work with MP3s, since the compression algorithm destroys the image. The track came out in ’99 but no one found the embedded image until now.