The problem that people had with the CD Walkman was that you had to carry around the CDs that you wanted to listen to. This meant that if you didn’t take a certain album or single out with you, you didn’t have the option to listen to it. Taking your entire CD collection just wasn’t practical. The evolution of mp3 players and iPods addressed this issue – now you could carry a huge library of music around with you in your pocket or the palm of your hand. But this still poses a problem – you are limited to the music that you happen to have downloaded and synched to your device at any one time.