A DJ from a smooth jazz station asked his program director why Bruce Hornsby And The Range's "The Valley Road" was on the playlist. The program director's response: "Familiarity...Without it, you're dead." After I mentioned this to a co-worker at another job, the co-worker responded, "John Denver's 'Thank God I'm A Country Boy' is a familiar song to most people, but you wouldn't expect to hear it on a smooth jazz station."
I couldn't argue with that.