In the early sixties youth carried music around in the palm of it's hand in the form of transistor radio, stations playing the latest rock and roll hits to satisfy the "kids" . Phil Spector listenned to each song he produced with his tradmark wall of sound to ensure it sounded good on a transistor radio, because that was his sales window. If it sounded good on radio then the market would buy it.
Radio has progressed through MW to FM to DAB and portables are part of your average phone either i the form on an inbuilt tuner using the headphone wires as an aerial or streaming media , which is effectively data that your supplier will charge you for. So the kids are still listening to music on portable devices that can be held, it's just now they have a little more choice and control and they are paying for it.
Ironic ,fifty years on,that a phone costing maybe seven or eight hundred pounds is being used for the same purpose as a cheap transistor radio. Though I am well aware that todays phones are actually very powerful computers but it's still quite amusing.