Philadelphia ? When Itai Adi’s friend Maria is calling, his cell phone lets him know by playing the Black Eyed Peas’ “Let’s Get It Started.”

Calls from other friends of the high school senior might prompt “Toxic” by Britney Spears, G Unit’s “Stunt 101,” or Usher’s “My Boo.”

And when his family is on the line? “I try to find an annoying ring for them,” says Adi, 17, who by latest count had downloaded 30 songs to ring on his cell phone, paying as much as $1.49 a shot. “It could either be a song I don’t like, or, since you can also download noises, it could be a bird that squawks really loud.”

It’s all sweet music to the ears of the downbeat record industry. Since catching on late last year, ringtones have exploded in popularity, producing an estimated $375 million in U.S. revenue this year, according to IDC, an information technology firm. The year before: only $18 million. Worldwide sales are far bigger, particularly in Asia and Europe.

Billboard magazine, known for charting most popular songs, introduced a ringtones category in November. The Billboard Music Awards last month picked its first Ringtone of the Year Award.

For those who think ringtones are like, so last year, how about ringbacks? They’re more like next year.

Ringbacks are songs or noises other people will hear when they call you. Instead of rrring, rrring, rrring, they could be hearing barnyard noises, Beastie Boys tunes or Beethoven. The owner of the phone gets to decide what callers will hear.

In December, T-Mobile launched the first U.S. ringback service. Verizon Wireless is test-marketing them in some western U.S. markets for $1 a month, plus $1.99 for each ringback song used. Sprint is expected to launch its service early next year.