The only synchronization I used to believe in was that all the stations in town did their commercial block at the same time. That way, you couldn’t jump up and down, all around the dial, and avoid them.
My local FM rock station has an afternoon show called the Men’s Room. Though based in Seattle, their show is syndicated throughout the US. Much of their show is call in talk and they get callers from all over the US. The last time I was in Phoenix I picked up the show on a local station. I noticed after a bit is was the same show they broadcast live the day before in Seattle.
Looks like Sirius XM satellite radio (the only music stations I listen to any more) also has music lists for each of the formats and the DJs only record inserts to provide commentary on the stuff that a programmer has pre-selected.
I saw a reference online claiming that “a select few” Sirius DJs pick their own music, but don’t know who those folks might be.
In prehistoric days when I worked as a DJ at a small market station there was a hybrid system, where songs from giant reel tapes representing two different formats were alternated with current hits and oldies (which you got to pick). For certain specialty shows there was a library of LPs and you’d make your own selections from those. The next place I worked was strictly automated, though an enterprising person running the board could sneak his own cassettes into the machines especially late at night, though of course I would never have done such a thing.
And they wonder why radio audiences are decreasing.
SiriusXM has too much talking for me. So what if it is “commercial free”, it sure ain’t voice free. And their selection is very small. I used to listen to radio all the time, now, never. I have a thumb drive for my car. No bad songs, no talking.
One of them was the aforementioned Jim Ladd. His “Headsets” program was always a winner.