"In the 60's, there weren't that many radio stations. Like five of them would be playing stuff like Frank Sinatra all the time... and there was one that played rock n' roll, for the most part. But really, they would just play whatever was popular at the time. So if by a fluke, a jazz record became a hit, they would play it. But in the late 60's, fm came out. And the heavier stuff- you know, drug songs, Led Zepplin and loud guitars- the fans of that stuff listened to fm more. So it became a circuit of two directions; fm versus am, and thus the 33s versus 45's. Then in the 70's disco came out and screwed everything up. By the 80's. there were all these new littler statopns that would take up a very specific niche in the world. You've got stations for oldsters, like CBS. You've got stations for kids, like Radio Disney. And there are stations for teens, like z100. But the problem is, each system makes up a playlist of about 500 songs that they just play all the time, in their respective little niches. And it ends up making more sense to just buy an iPod, that way you can just pick the same 500 songs to listen to all the time. And the problem with less people listening to the radio and using their ipods more, is: how are people supposed to get exposed to new music?"
The History of Radio