First I need to point out that I first read this idea in a Robert Heinlein book, The Number of the Beast. I'm probably not average in my radio listening habits since I only listen to it for information, rather than music but I think this idea could be applied to either case.

Each segment would be accompanied by a small chunk of digital data that includes title, author, keywords, and some kind of start/end tags. The audio itself could be either in a digital format or as a standard radio transmission. The first would probably allow radios to transmit more info/music, while the second would maintain backward compatibility.

New radios would be developed that could be programmed to the users tastes. Maybe a list of keywords that the radio would listen for, or particular shows or composers or speakers. Whenever the radio found something that matched the users list it would be recorded. At some point memory would fill up and older or less desirable shows would be deleted to make room for new ones.

This would continue even when the listener wasn't listening. For example, I never listen to the radio at work, but when I get in the car it would be great if the last two or three traffic reports were sitting there waiting for me to listen to them. Even better would be if I could specify those roads that I was actually going to be using, and only reports for those roads would be recorded.

In addition to all of the 'user specified' audio, there should be an option to record a certain percentage of random stories/songs/items.