In general, the items least valuable to the audience are played before a sequence of commercials, and the most valuable items are played after those commercials. To reduce station changes, commercial breaks are made as brief as commercially possible, and the valuable item following a commercial is rotated several times per hour. Commercial breaks may be longer at times when the audience is thought to be larger. In some countries the maximum time given to commercial breaks is regulated.
Dead air time is considered wasteful. It neither produces profits, nor draws more audience.
Music radio has been helped by the development of semi-automated song-picker programs. Basically, these present the disc-jockey with a list of commercially-acceptable music selections, and other items for the current time slot. These give the disc-jockey some artistic freedom to select songs, promotions, jingles, etc., and yet still assure a cohesive station "sound" and good audience satisfaction. They also reduce a disc-jockey's workload, allowing him or her to develop news items, run the station, prepare gags, or take call-ins while a song is playing. The employer may as a result reduce staffing levels and thus trim overhead costs.
A station's value is usually measured as a percentage of market share in a market of a certain size. The measurement in U.S. markets has historically been by Arbitron, a commercial statistical service that uses listener diaries. Arbitron diaries were historically collected on Thursdays, and for this reason, most radio stations have run special promotions on Thursdays, hoping to persuade last-minute Arbitron diarists to give them a larger market-share. Stations are contractually prohibited from mentioning Arbitron on the air.
Some well-known music-radio formats are Top 40, Freeform Rock and AOR (Album Oriented Rock). It turns out that most other stations, classic, R&B etc. use a variation of one of these formats with a different playlist.
The original formulaic music radio format was "Top 40." In this 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.
Top 40 radio would punctuate the music with jingles, promotions, gags, call-ins, and requests, brief news, time and weather announcements and most importantly, advertising. The distinguishing mark of a traditional top-40 station was the use of a hyperexcited disc-jockey, and high tempo jingles.
Some of the most famous Top 40 stations of the era were Musicradio 77 (http://www.musicradio77.com) WABC/New York, 93 Boss Radio (http://www.bossradioforever.com) KHJ[?]/Los Angeles and Musicradio 89 (http://musicradiowls.musicpage.com/) WLS/Chicago.
Jingles are the musical equivalent of neon signs, and they can be remarkably beautiful. Jingles are brief, bright pieces of choral music that promote the station's call letters, frequency and sometimes disc-jockey or program segment. Jingles were produced for radio stations by commercial speciality services. The most famous jingle service was called PAMS (http://www.pams.com), based in Texas.
Gags are audible jokes, often with a (sometimes imaginary) side-kick. Talk radio evolved out of gags.
News, time-checks, real-time travel advice and weather reports are often quite valuable to listeners. The news headlines and station identification are often given just before a commercial. Time, traffic and weather are given just after. The engineer typically sets the station clocks to standard local time each day, by listening to WWV or WWVH (see atomic clock).
The station will usually have a policy of announcing time, station call letters and frequency as often as six times per hour, in order to build station loyalty. Jingles can very useful for giving the station a branded sound in a pleasant, minimal amount of air-time.
While small stations may simply "tear and read" news items (from the teletype), larger stations may employ an editor to rewrite headlines, and provide summaries of local news. The summaries allow more news to fit in less air-time. Some stations can share news collection with TV or newspapers in the same media conglomerate. An emerging trend is to use the radio station's web site to provide in-depth coverage of news and advertisers head-lined on the air.
Most radio stations maintain a call-in telephone line for use during promotions and gags, or to take record requests. Jocks generally answer the phone and edit the call during music plays.
Promotions are usually the on-air equivalent of lotteries for listeners. Promotional budgets usually run about $1 per listener per year. In a large market, a successful radio station can pay a full time director of promotions, and several lotteries per month of vacations, automobiles and other prizes. Lottery items are often bartered from advertisers, allowing both companies to charge full prices while incurring wholesale costs. For example, consider a cruise vacation. Cruising companies often have unused capacity, and when given the choice, prefer to pay their bills by bartering vacations. Since the ship will sail in any case, bartered vacations cost the cruise company little or nothing. The promotion is itself advertising for the company providing the prize.
"Top 40" was the original form of music radio. A later development was "freeform" Rock, later commercially developed as AOR (Album-Oriented Rock), in which selections from an album would be played together, with an appropriate introduction.
Traditional freeform rock stations prided themselves on offering their disc-jockeys freedom to play significant music and make significant social commentary and humor. This approach developed commercial problems because disc-jockeys attracted to this freedom often had tastes substantially different from the audience, and lost audience share. Also, freeform rock stations could lack predictability, and listeners' loyalty could then be put at risk.
Responsible jocks would realize their responsibility to the audience to produce a pleasant show, and try to keep the station sound predictable by listening to other jocks, and repeating some of their music selections.
At their best, freeform stations have never been equalled for their degree of social activism, programmatic freedom, and listener involvement. However, to succeed, the approach requires genius jocks, totally in-tune with their audience, who are also committed to the commercial success of the radio station. This is a rare combination of traits. Even if such people are available, they often command extremely high salaries. However, this may be an effective approach for a new station, if talented jocks can be recruited and motivated at low salaries.
AOR (Album Oriented Rock) developed as a commercial compromise between top-forties-style formulas and freeform rock. A program director or music consultant would select some set of music "standards" and require the playlist to be followed, perhaps in an order selected by the jock. The jock would still introduce each selection, but the jock would have available a scripted introduction to use if he was not personally familiar with a particular piece of music and its artist. Obviiously a computer helps a lot in this process.
Computer-directed playlisting was a God-send for AOR, because it gave the jocks a great deal of freedom, without risking the station's commercial stability. The result was often happier jocks, happier audiences, and higher ratings.
A wonderful, relatively safe compromise with the artistic freedom of the jocks is that a few times each hour, usually in the least commecially valuable slots of the hour, the disc-jockey can highlight new tracks that he or she thinks might interest the audience. The audience is encouraged to comment on the new tracks, allowing the station to track audience tastes.
A skillfully-run AOR station can be virtually indistinguishable from a top-quality freeform station with good jocks that listen to each other.
Giving a jock freedom to play a few new songs has other benefits. It increases the credibility of the station with serious listeners. Also, a willingness to identify and play new talent makes a radio station very valuable to record-promoters and artists. The promotional recordings let a station to develop a large, high quality music library at low cost.
To play new songs that honestly interest the audience, the station must publish rules about which promotional offers a jock should refuse. Otherwise commercial gifts, promotional offers and other payola can cause jocks to play bad songs, and ruin the station's ratings and profitability. A policy helps the jocks, because it gives them a simple reason to say no, so that they can continue to do a good job without offending promoters.
Not playing new artists has been described as a weakness of "classic rock" or "oldies" formats. This is true in a creative but not a commercial sense. One of the unwritten "rules" of commercial radio is to get a big share of ratings and revenue. Stations will not get these if they frequently play songs unfamiliar to their audience. This is why "Top 40" stations played only the biggest hits and why oldies and classic rock formats do the same for the eras they cover.
The oldies and classic rock formats have a strong niche market, but as the audience becomes older the station becomes less attractive to advertisers. Advertisers perceive older listeners as set in their brand choices and not as responsive to advertising as younger, more impulsive listeners. Oldies stations must occasionally change to more youthful music formats.
This preference for younger listeners caused the decline of the "Big Band" or "Standards" music formats that covered music from the 1930s to the 1950s. As the audience grew too old for advertisers, the radio stations that carried these formats saw a sharp loss of ratings and revenue. This left them with no choice but to adopt more youthful formats.
These formats all have small but very loyal audiences in the largest markets. Most follow formats similar to the above (Top 40s, Freeform, AOR and Oldies), except with a different playlist. Public service stations following these formats tend to be "freeform" stations.
Some music radio is broadcast by public service organizations, such as PBS or the BBC. These usually resemble freeform stations, with particular programs for different types of music. More popular formats get more popular hours. The Avant-garde programs tend to be pushed to the late night and early morning slots.
Music radio is also a means of promoting other enterprises, such as a record label or ad-hoc music events in which the broadcaster(s) have a commercial interest.