Top 40, Contemporary Hit Radio (CHR) is a popular radio format that primarily features the latest hits in pop music, typically including the top 40 songs on the current charts. This format emerged in the mid-20th century and has evolved to engage listeners through music variety, and interactive audience participation. Stations often utilize research data to curate playlists that reflect listener preferences, ensuring a mix of familiar hits and new releases. Top 40 is a list of the 40 currently most popular songs. It is the best-selling or most frequently broadcast popular music. Record charts have traditionally consisted of a total of 40 songs. Some national syndicated radio shows, such as American Top 40, featured a countdown of the 40 highest-ranked songs. A CHR station plays a significant amount of current popular music. This format is the descendent of the Top 40 stations popular from the 50’s through the 80’s. Although some CHR stations base their playlists on surveys of local record sales or phone requests, most rely on published charts such as the Billboard Hot 100. Contemporary Hit Radio stations tend to concentrate on specific music styles, such as Rock/Pop/Dance or R&B/Rap/Dance. Some stations play a significant amount of hits released during the past ten or fifteen years.