These living letters were meant to be sent in the mail and even came in plastic, mailable cases. How wonderful! I wonder if something like this is what the "Abominatron" explanation was recorded on that Bob Moog sent to Herbert Deutsch?
I was trying to find a clip of that to play for you here, but I can't seem to find one online. Well, you can listen to one on the iTunes website here:
It's track number two. I do suggest buying the track though, it is well worth the 99¢.