Yes, even when I worked at an NPR affiliate station 10-15 years ago, automation like this was common. You could even set up lists of songs by theme ("evergreen", "newly released", "big in the last 6 months", "seasonal") and the software would rotate through them (avoiding playing songs too often or too infrequently as configured), pre-recorded underwriting/PSA's/promotions, station ID breaks, etc. It would even select tracks and subtly slow down/speed up tracks to hit a deadline as needed so that it could, for example switch to live or syndicated programming exactly on the hour without a noticeable interruption.

> subtly slow down/speed up tracks to hit a deadline as needed

Jesus, I've always suspected this (listening to the radio and a song just feels a little wrong) but never had confirmation. What's that "feature" called?

Some names came to mind. The company that made the most common software that I can remember seeing was called ENCO; it appears that their current offering in that vein is called MusicMaster[0].

[0] https://www.enco.com/products/musicmaster

I don't remember, it was one of an enormous number of settings in a very complicated piece of software (and a decade ago when I was last exposed to it). The stretching was usually very minimal, on the order of ~10 seconds over an hour, so ~0.3% max (the rest of the timing would be managed by selecting tracks with appropriate lengths).

We had a local AM station here that the guy broadcast from his laptop in his RV, sending the stream via the internet to the transmitter. So, don't be surprised of some really are run from somebody's laptop...