Modern methods of modulation, using a combination of amplitude and phase with error correction, can carry several bits in one cycle of the carrier. Basically, it is a matter of having various distinguishable shapes for the wave, and mapping each to a number.
http://www.physics.udel.edu/wwwusers/watson/student_projects/scen167/thosguys/qam.html
You could probably store 3 minutes of CD quality (16/44.1) sound on a 3 minute 78. Maybe even 24-bit sound.
Ah, but in time the encoding scheme will have been lost and then how will it be reconstructed? The archeologists of the future will be at a loss.
(On the other hand, the chronologists of the present may be lost with your post; it carries yesterday's time stamp.)
Mike -- mrichter@xxxxxxx http://www.mrichter.com/