oldies76 said:
Everyone enjoys their own songs and that's the way of life...
Yes, but the commonality of, let's say, 70% of the songs, is undeniable. So a station finds the songs that are common to just about everyone in their market, eliminates the ones that are not, and plays them.
There is a radio truism that is more often applied to new music that says, "you can't be hurt by what you don't play." Listeners don't talk about the songs you don't play... but they complain vigorously about ones you do play that they don't like. In fact, probing when a listener complains about repetition yields the fact that the station plays quite a few songs that the listener does not like... thus "repetition" of bad songs. They don't complain about a song they love being played very often.
You make it sound like there's a "master list" of songs that everyone must like and listen to. Sorry, but I disagree.
There
is a master list, and it's the one with Brown Eyed Girl near or at the top. A lot of the songs are found on every list of tested songs (assuming the target age is the same) everywhere. The factors that change some songs would be things like ethnicity and, thus, ethnic influence on the market, history of oldies stations in the market (local over- or underplay), the rest of the competitive array that shares listening with an oldies (or classic hits) station, etc.
A change in rank of even 100 or perhaps 200 positions is not significant, and that is because rotation is not determined by such differences... a station with 800 titles might have 3 or 4 rotational categories, heavy, medium, light and fill/very light for example. So all the songs ranked, again in an example, 150 to 400, might get the same rotation whether they were the 150th or the 400th song. (There are other criteria, like a PD making an "artistic" decision that certain songs don't bear up as well to repetition as others, thus they are slowed down)
Based on that kind of broader categorization, you can say that there is truly a common song list that in all probability works everywhere, while there is a secondary list of songs that may work fine in some places, marginally in others and not as all in others.
But the list is not one of songs people "must" like, but rather of songs that just
are liked or are seen as positive everywhere.