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Like so many of our musical questions, the answer is that the melodies aren't always the same—they just sound alike. And the chorus of people isn't always the same—they just sound alike. But two fascinating questions arise: Why do they sound alike, then, and why are they sometimes exactly the same?

As far as I can glean from my Aeron chair, the story begins in Texas. Since the dawn of commercial radio, songs had been used to sell products, and NBC (following the lead of Atlanta's WSB) had used a sequence of three chiming notes struck on a xylophone to provide a sonic identification for its programming. The earliest singing call-letter tunes are traced to KLIF's Bill Meeks, a Dallas musician who wrote jingles and other incidental music for two on-air bands. He broke away from broadcasting in 1951 to form a company called PAMS—Promotion Advertising Merchandising Service. Its pitch was that the ratings system in place for radio didn't tell the whole story. Advertisers got good response from ads on low-rated stations. The reason, PAMS suggested, was that listeners didn't know what station they were listening to, so the information didn't get reported accurately to the ratings service. If there were memorable call-letter spots, the station could in effect advertise itself, improving the accuracy of ratings reports and allowing it to charge more for advertising, in the familiar snake-eats-itself cycle of life.

The natural way to do that is to use the "station ID," the FCC-mandated announcement of a station's call letters that occurs at regular intervals throughout the broadcast day. PAMS, in effect, was helping stations brand themselves by creating an aural logo—a tune. The station's call letters could be hummed, which made them more memorable. According to PAMS' own history, the company created a group of 10 demonstration jingles, called "Series 1," in the early '50s, and shopped it around to Texas stations. The idea was that the stations would pick the demo they liked and submit copy (call letters and any other phrases) that fit within its structure. PAMS used the instrumental backing tracks already laid down for the demo, and laid a new custom vocal track featuring those harmonizing singers over it. Presto—syndicated station-identification jingles. It's still done the same way today. So if you hear two different stations in different markets using the same melody and singers for their jingles, it's because they bought them from a syndication outfit.

As Top 40 radio started to rule the airwaves in the late '50s, the PAMS-style jingles became even more crucial to stations battling it out in crowded, lucrative markets. Chuck Blore, a program director from El Paso, pioneered a ubiquitous-identification strategy he called "Color Radio" (by analogy with then-novel color television) for L.A.'s KFWB "Color Channel 98." DJs and music were pushed into secondary positions on the air, and the starring roles were filled by jingles, promos, news briefs, weather reports, and other layers of station-specific material. According to his memoirs, Blore wanted promos that sounded like West Side Story, with big orchestration and big, jazzy choral arrangements. And each promo would end with the station call letters sung in the same distinctive chords and rhythm. The Color Radio notion was syndicated to other big markets, and jingles were produced centrally and syndicated as described above.