What you are getting at is that people listen to different stations because they are different... but within the range of music tastes of each listener.In LA and Dallas Audacy owns both classic and variety hits stations (KRTH and KCBS).
The way to handle it is by adjusting percentages. There are enough songs that you can do that.
People here are freaking out when they hear songs that might not fit. But they're taking those songs out of context from the rest of the format.
The PPM revealed that listeners often had two or three favorite stations, and the use of each varied by the day, the week and over time. Not a lot of non-proprietary research has been done in this area but I can say that choices vary by things like mood, intensity of work performance, social environment and the time of the day.
Generally, listeners that have a variety of stations they use "a lot" pick different formats. In some markets, you might see a classic hits, an AC and a country station sharing top preferences. Or a CHR, Hot AC and AC station. There are some who flip between identical formats in markets where there is such a thing, but that is not the main reason for different choices.
My first experience with overlapping playlists was 62 years ago during my internship in Mexico City. Two of the stations played what we'd call Top 40. One played all Spanish songs, the other played about half and half Spanish and English Top 40 hits; the all-Spanish language music station played a slightly different blend of those songs. The operator of those stations did do research and found that the listeners to one did not like the other; there was no sharing or splitting of audience at all. And both were very highly rated. The all-English song station did better in upper income listeners, and the all Spanish music one was stronger in middle to upper-low income listeners.