In 1980 I worked in local radio.
The playlist was set by corporate (or by a consultant). You could maybe change the order of the songs, but you were not allowed to add / subtract any songs.
By 1980 over 1/2 of the stations were "automated". Music was provided by a service, on Reel to Reel tape (played by Revox B77's).
Path to a radio job in 1980? A Third Class RadioTelephone License with Broadcast Endorsement.
An aside...
The automation machine at one station I worked at had 2047 programmable steps. (well, 2048, 0 was a step)
As a 16 year old, I could not fathom why it was not 2400. With 2400 steps, you could program each hour the exact same; not so with 2047.
Editing was a dream on the ASR33 teletype. Seems scissors and tape are very effective.