Recording and playback of sound was first achieved by Thomas Edison in 1877. His first recording was the nursery rhyme "Mary Had a Little Lamb." (If Edison believed it was going to work, he might have said something more momentous.) Edison patented his "talking machine," or phonograph, in 1878. Nearly deaf, he noticed that each sound had a distinct vibration, and by etching or indenting those vibrations in a physical material, they could be retraced and replayed. The first phonograph combined previously existing technologies to record and play sound by mechanical means. He used a trumpet to gather sound and concentrate it, causing a taut membrane at its smaller end to vibrate like a drumhead (i.e., a diaphragm). A stylus attached to the diaphragm indented a hill-and-dale pattern (created by the sound vibrations) on a moving surface (initially a cylinder) of a malleable...