The inaugural top ringy-dingy choice goes to ... (drum roll) ... "My Boo" by Usher and Alicia Keys.

It inspired 97,000 purchases last week.

By contrast, the No. 1 legal song-download of the week — U2's "Vertigo" — drew 25,000 buyers.

Ring tones are outselling legit song downloads by more than 3 to 1, even though those nagging tones tend to cost almost twice as much ($1.99 versus a buck) and don't give the listener the actual tune, only a rinky-dink imitation.

According to Billboard chart czar Geoff Mayfield, the magazine started tallying ring-tone purchases because "it's a very important new revenue stream for the industry."

The mobile-music market adds up to roughly $300 million in the United States so far, Mayfield said. Four million consumers are "active" users, meaning they switch their ring tone at least once a month. Tens of millions are "occasional" users — those who tend to keep the same tone for a six month period. Internationally, the market for ring tones is $3.1 billion.

In contrast to games and other information services available on cell phones, "everyone has some kind of ring tone, and most people want to choose theirs," according to Adam Zawel, an analyst for the Yankee Group.

And Mayfield expects a second growth spurt when the industry rolls out its next innovation — "mastertones," featuring the actual recording rather than today's sonic mimic.

Europe and Japan are ahead on mastertone technology, but some American cell phones allow their owners to download songs directly from their players, letting them make their own ring tones.

Mayfield says another reason Billboard decided to highlight ring tones is that "they offer an indication of just how vital music remains in the minds of consumers."

After all, by purchasing a ring tone, you're showing your identification with an artist or song. The service gives fans a quick, if strident, way of announcing their musical taste to the world. A purchase also means that the listener wants to hear a given song over and over again.

According to Michael Gartenberg, a technology analyst for Jupiter Research, this trend measures the increasing "personalization of the cell phone. It has become such a part of people's lives that the No. 1 thing they want with them when they go out is a cell phone. And the No. 1 thing they want to do when they're outside is make a phone call."

The data for Billboard's Hot Ringtones chart come from a wide variety of distributors and wireless carriers — enough, according to the magazine, to cover more than 90 percent of the American market.

The most popular ring tones in the United States now come overwhelmingly from the world of hip-hop, which indicates the youthful market for singing cell phones.

Believe it not, the No. 13 Top Ringtone is Vanilla Ice's reviled, old number "Ice Ice Baby."