Page "Music radio" Paragraph 26

The original formulaic radio format was Top 40 music.

In this radio format, disc-jockeys would select one of a set of the forty best-selling singles ( usually in a rack ) as rated by Billboard magazine or from the station's own chart of the local top selling songs.

In general, the more aggressive " Top 40 " stations could sometimes be better described as " Top 20 " stations.

They would aggressively skirt listener boredom to play only the most popular singles.