Although these systems were originally implemented by manual index card methods, since the late 1970s they have exploited the efficiency and speed of digital computers.
These systems are databases of the songs in active rotation at a radio station, plus an ample set of rules for sequencing them in accordance with specific policies.
Many people believe[vague] that disc jockeys at radio stations are responsible for choosing the music which is heard on their shows.
In reality, playlists for each hour of the day have usually been generated in advance by a radio station's program director using a music scheduling system.
When considering the internet as a new broadcast medium, the definition of scheduling could be broadened "to curate or arrange a linear playlist of video/audio content for live transmission or on-demand distribution."