You absolutely need to make time to watch these three short videos (9 minutes total). It is about the invention of sound recording, the technological changes in sound recording, interviews with Edison and his assistant, etc. etc. Wax cylinders, tinfoil, Victrolass', etc. Most of these video content is many decades old. http://www.youtube.com/watch?v=_C6noBmD0cw http://www.youtube.com/watch?v=Wmg0BD_rR6Y&NR=1 http://www.youtube.com/watch?v=qGJR2DZBfF0&NR=1