Recurrent rotation refers to a group of songs still frequently aired on a contemporary hit radio station several months or even years after the initial debut. It is also used to describe core songs in other radio formats as well. Most charts have special rules to determine when a song has become recurrent, at which point they are removed from current charts (such as the Billboard Hot 100) and placed on special "recurrent charts." Recurrent charts tend to be more static, with less week-to-week changes in popularity, than current charts.
The Billboard charts include these lists:
Songs that survive in recurrent rotation typically form the basis of radio formats as years advance. A hit song that is left out of recurrent rotation will eventually become known as a "forgotten 45," a name derived from the fact that singles used to be released on 45 RPM records.