Back when the world was analog, we listened to cassettes, and carried portable audio cassette players with pride. Yesteryear's Walkmans were indispensable, allowing us to take our beloved mix tapes everywhere. But the equipment was overthrown. First came the Discman, then the iPod. A new vocabulary developed"MP3s," "iTunes playlists"and before you could hit pause, words like "rewind" had lost all meaning.