Now, progress is a more slippery, nuanced process. A piece of technology becoming available to the public, or cheaper, or smaller, or faster, or sometimes all at once, is often the earth-shattering event. But obviously, no one object has changed more than the iPod. Taking MP3s out of the computer and into a portable device with headphones didn’t just put a nail in the CD’s coffin, it killed the Discman and the Walkman instantly. And the store Apple used to sell music for your iPod, iTunes, completely revolutionized the business, doing major damage to physical music stores in the process.