oldies76 said:
Library and Playlist, two different terms here.
This is a word usage issue.
In broadcasting, it might be considered that the active library
is the playlist.
The key is understanding that the "playlist" term comes from the era when stations might have a true "playlist" of songs that could be played; if it was not on the list, it could not be played.
The introduction of computerized music logs in the late 70's (yeah, using anything from S-100 machines to TRS-80's and Apple II's) made "playlist" and "active library" essentially the same... the DJ could not play anything but what was on the log.
Stations may have a music archive of some kind for songs that they don't have on in the active library. Some companies have centralized systems where nearly anything that might be played on the radio is kept; a station needing a song for a morning show bit or a special can pull them from the central server.
In any case, for most of the discussions here, we have several elements:
1. The active library that includes the songs that come up time and again in the 6 AM to 7 PM time where most listening and nearly all revenues come from.
2. Specialty show songs that play generally in hours that don't produce much revenue and listening, but which are an opportunity to enhance the brand in particular subsets of the audience.
3. Additional songs used to fill or pad overnights or even late nights. Often, these are songs that don't fit, based on score or style, the focus during the prime sales hours.
Here is the math of exposure based on 25-54 averaging at a certain classic hits station in New York (caveat: these are broad averages to not violate citing specific books):
Total people reached 6 AM to Midnight, all week: 1.8 million
Percent of all 25-54's reached in a week: 21%
Total people reached daily on average: 500,000
Percent of all 25-54's reached each day: 6%
Total people reached 5 AM-7 PM M-Sun: 1.6 million.
So you see that evenings are only a small contributor to the reach of the station, and weekend evenings are even less.
Overnights cumes 100,000 so that means that songs played in that daypart that are not otherwise played reach only a tiny group. Weekend evenings reach about 80,000 each... less even than overnights. So plays in weekend evenings reach to few people to matter.
All this is why many, if not most, of us look at M-F 6 AM to 7 PM or M-F 6 AM to Midnight for analyzing music plays; we don't look at weekend evening and we don't look at overnights as they don't represent many impressions, even if songs are played.