Most modern radio stations are digital, but in the "old" days, actual tape cartridges (CARTS) were used for pre-recorded broadcasts. The term is still used, although modern carts are in digital or CD form. CARTS are made in the radio or recording studio and involve the recording of voice and music to produce a finished advertising spot for broadcast. When it's time to air the advertisement, the radio announcer chooses the proper CART and plays the advertisement. Larger companies use independent recording studios to produce CARTS and distribute them to radio stations from which they have purchased advertising space.
Radio shows, interviews and news programs that are syndicated (broadcast on multiple stations) are produced primarily in recording studios but may be produced in a radio station equipped with the necessary equipment. Production of syndicated shows uses similar recording techniques and equipment as those used for music, and include microphones, mixing consoles and recording devices. Editing of the show and sound enhancement is done in the last steps of the production process, and the finished product is sent to the radio stations for broadcast via digital file or CD.
Jingles are also produced in a recording studio, but one equipped with musical instruments, and employing songwriters, singers and musicians. There are many companies throughout the country that write, perform and record jingles and longer pieces of music for commercial radio, television and movies.
During live radio broadcasts, the radio host is often assisted by one or more engineers in the live production of the show. Production duties include checking and adjusting sound levels during the show, sound effects during talk shows, the timely preparation and playing of advertising CARTS, news breaks and jingles, and following a schedule of announcing station "call letters." In commercial radio production, everything is scheduled to the second, so no "dead air" is heard by the listener. Hosts and engineers are pre-instructed on what to say and play during the broadcast, and are responsible for all aspects of producing a "seamless," professional show.
Radio stations often employ interns to help out in the broadcast studio, which will allow firsthand experience in observing what goes into commercial radio. There are schools specializing in broadcasting, and a number of colleges also offer courses for those seeking to learn the radio business. While it isn't always necessary to have a certificate or degree in order to break into the radio business, formal education on the latest trends, equipment, procedures and techniques will improve your chances.