Don't forget the type of music. Album oriented stations were so much better than AM.I forgot to mention the transition from AM to FM. In 1970, only hippies and dentists offices had FM. Once the FM radios started being standard equipment in cars, it was remarkable how quickly everyone moved from AM to FM. By 1975, almost everyone was listening to FM instead of AM. Less noise, frequency response to 15k, and stereo, were the big changes in fidelity. This was a big one.