WKNR "Keener 13"---switching to night-time transmitters

One thing I remember about about growing up in Toledo (Ohio) is listening to a radio station---WKNR ("Keener 13") out of Detroit (/Dearborn).

In particular, the way I would either lose reception altogether---or still be able to pick their signal up, but it would fade in-and-out while sharing their frequency with other signals and, thus, be unlistenable---after they switched over to their "night-time" transmitters at a designated time in the early evening.

I remember that, between 1967 to 1972 (on-and-off), they would switch during whatever song was playing at the designated "switching time".  What they did was---they didn't switch just anywhere during the song ...they were "clever" about it.  They would hit-the-switch after, say, the first or second verse of the song---or, maybe, just as the chorus to one of the verses was approaching. 

Somehow I was always fascinated by this "formality" that probably went largely unnoticed by most at the time.  And how the station still stuck with this general pattern just the same.

I've always wondered if I was the only casual listener who noticed this particular practice of theirs.