Also AM Radio was the “TV” of it’s day
From the late 20s till the early 50s, AM radio was, what “TV” is today.
After TV came into fashion and became affordable, AM radio had to find another source of programming.
This involved a shuffle of sorts.
AM was best suited when radio served what “TV” does today. Since it was mostly talking shows, it needed minimal fidelity with a large service area. AM does this great.
FM was blocked by AM radio, who coincidently were not so keen on TV, as were the movies not so keen on it.
After the shuffle of the early 50s and TV won out, AM had to find a niche. Since most people still had receivers of AM, the natural market was music.
But AM was not well suited for music. So it took a decade or so for music to shift to the FM band. Remember AM radio stations had a huge investment going back to the late 20s. They weren’t going down without a fight.
But with FM stereo and more FM stations being built it was obvious AM would eventually lose out. Most AM stations handled this simply by buying or affiliating with FM stations of their own.
But this left a gap, what to do with AM Radio? It was still there. Well News, Sports and Talk eventually filled this gap.
But it took awhile, as I said, no one was going down without a fight. I recall in a big city like Chicago, even into the mid 80s we still had AM radio stations playing pop music